Index: branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/FixedValueParameter.cs
===================================================================
--- branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/FixedValueParameter.cs	(revision 17461)
+++ branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/FixedValueParameter.cs	(revision 17532)
@@ -34,4 +34,9 @@
     IItem IFixedValueParameter.Value { get { return Value; } }
 
+    public override T Value {
+      get => base.Value;
+      set => throw new NotSupportedException("FixedValueParameters do not support setting their value.");
+    }
+
     public override void ForceValue(T value) {
       throw new NotSupportedException("FixedValueParameters do not support setting their value.");
Index: branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/HeuristicLab.Parameters-3.3.csproj
===================================================================
--- branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/HeuristicLab.Parameters-3.3.csproj	(revision 17461)
+++ branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/HeuristicLab.Parameters-3.3.csproj	(revision 17532)
@@ -127,4 +127,5 @@
     <Compile Include="OptionalConstrainedValueParameter.cs" />
     <Compile Include="Plugin.cs" />
+    <Compile Include="ReferenceParameter.cs" />
     <Compile Include="ScopeTreeLookupParameter.cs" />
     <Compile Include="ValueParameter.cs" />
Index: branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/ReferenceParameter.cs
===================================================================
--- branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/ReferenceParameter.cs	(revision 17532)
+++ branches/2521_ProblemRefactoring/HeuristicLab.Parameters/3.3/ReferenceParameter.cs	(revision 17532)
@@ -0,0 +1,201 @@
+﻿#region License Information
+/* HeuristicLab
+ * Copyright (C) Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ *
+ * This file is part of HeuristicLab.
+ *
+ * HeuristicLab is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * HeuristicLab is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ */
+#endregion
+
+using System;
+using System.Drawing;
+using HEAL.Attic;
+using HeuristicLab.Common;
+using HeuristicLab.Core;
+
+namespace HeuristicLab.Parameters {
+  [Item("ReferenceParameter", "A base class for reference parameters that forward to other (referenced) parameters.")]
+  [StorableType("39CE4123-E41C-4935-90FE-91F6A629178A")]
+  public abstract class ReferenceParameter : Parameter, IValueParameter {
+    public override Image ItemImage {
+      get {
+        if (Value != null) return Value.ItemImage;
+        else return base.ItemImage;
+      }
+    }
+
+    public IItem Value {
+      get => GetActualValue();
+      set => SetActualValue(value);
+    }
+
+    [Storable]
+    public IValueParameter ReferencedParameter { get; }
+
+    public bool ReadOnly {
+      get => ReferencedParameter.ReadOnly;
+      set => ReferencedParameter.ReadOnly = value;
+    }
+
+    [Storable(DefaultValue = true)]
+    private bool getsCollected;
+    public bool GetsCollected {
+      get { return getsCollected; }
+      set {
+        if (value != getsCollected) {
+          getsCollected = value;
+          OnGetsCollectedChanged();
+        }
+      }
+    }
+
+    protected ReferenceParameter(IValueParameter referencedParameter) : this(referencedParameter.Name, referencedParameter) { }
+    protected ReferenceParameter(string name, IValueParameter referencedParameter) : this(name, referencedParameter.Description, referencedParameter) { }
+    protected ReferenceParameter(string name, string description, IValueParameter referencedParameter) : this(name, description, referencedParameter, referencedParameter.DataType) { }
+    protected ReferenceParameter(string name, string description, IValueParameter referencedParameter, Type dataType) : base(name, description, dataType) {
+      ReferencedParameter = referencedParameter ?? throw new ArgumentNullException("referencedParameter");
+      RegisterEvents();
+    }
+
+    [StorableConstructor]
+    protected ReferenceParameter(StorableConstructorFlag _) : base(_) { }
+
+    [StorableHook(HookType.AfterDeserialization)]
+    private void AfterDeserialization() {
+      RegisterEvents();
+    }
+
+    protected ReferenceParameter(ReferenceParameter original, Cloner cloner) : base(original, cloner) {
+      ReferencedParameter = cloner.Clone(original.ReferencedParameter);
+      RegisterEvents();
+    }
+
+    private void RegisterEvents() {
+      ReferencedParameter.ToStringChanged += (o, e) => OnToStringChanged();
+      ReferencedParameter.ItemImageChanged += (o, e) => OnItemImageChanged();
+    }
+
+    protected override IItem GetActualValue() {
+      return ReferencedParameter.ActualValue;
+    }
+    protected override void SetActualValue(IItem value) {
+      ReferencedParameter.ActualValue = value;
+    }
+
+    public override string ToString() {
+      return Name + ": " + (Value != null ? Value.ToString() : "null");
+    }
+
+
+    #region event handlers
+    // code for forwarding of events adapted from https://stackoverflow.com/questions/1065355/forwarding-events-in-c-sharp
+    private EventHandler valueChanged;
+    public event EventHandler ValueChanged {
+      add { // only subscribe when we have a subscriber ourselves
+        bool firstSubscription = valueChanged == null;
+        valueChanged += value;
+        if (firstSubscription && valueChanged != null) //only subscribe once
+          ReferencedParameter.ValueChanged += OnReferencedParameterValueChanged;
+      }
+      remove { // unsubscribe if we have no more subscribers
+        valueChanged -= value;
+        if (valueChanged == null) ReferencedParameter.ValueChanged -= OnReferencedParameterValueChanged;
+      }
+    }
+    private void OnReferencedParameterValueChanged(object sender, EventArgs args) {
+      valueChanged?.Invoke(this, args); // note "this", not "sender" as sender would be the referenced parameter
+    }
+
+    private EventHandler readOnlyChanged;
+    public event EventHandler ReadOnlyChanged {
+      add { // only subscribe when we have a subscriber ourselves
+        bool firstSubscription = readOnlyChanged == null;
+        readOnlyChanged += value;
+        if (firstSubscription && readOnlyChanged != null) //only subscribe once
+          ReferencedParameter.ReadOnlyChanged += OnReferencedParameterReadOnlyChanged;
+      }
+      remove { // unsubscribe if we have no more subscribers
+        readOnlyChanged -= value;
+        if (readOnlyChanged == null) ReferencedParameter.ReadOnlyChanged -= OnReferencedParameterReadOnlyChanged;
+      }
+    }
+    private void OnReferencedParameterReadOnlyChanged(object sender, EventArgs args) {
+      readOnlyChanged?.Invoke(this, args); // note "this", not "sender" as sender would be the referenced parameter
+    }
+
+    public event EventHandler GetsCollectedChanged;
+    private void OnGetsCollectedChanged() {
+      GetsCollectedChanged?.Invoke(this, EventArgs.Empty);
+    }
+    #endregion
+  }
+
+
+  [Item("ReferenceParameter<T>", "ValueParameter<T> that forwards to another (referenced) ValueParameter<T>).")]
+  [StorableType("6DD59BE5-C618-4AD4-90FE-0FAAF15650C3")]
+  public sealed class ReferenceParameter<T> : ReferenceParameter, IValueParameter<T>
+    where T : class, IItem {
+
+    public new T Value {
+      get => ReferencedParameter.Value;
+      set => ReferencedParameter.Value = value;
+    }
+
+    public new IValueParameter<T> ReferencedParameter { get => (IValueParameter<T>)base.ReferencedParameter; }
+
+    public ReferenceParameter(IValueParameter<T> referencedParameter) : this(referencedParameter.Name, referencedParameter) { }
+    public ReferenceParameter(string name, IValueParameter<T> referencedParameter) : this(name, referencedParameter.Description, referencedParameter) { }
+    public ReferenceParameter(string name, string description, IValueParameter<T> referencedParameter) : base(name, description, referencedParameter) { }
+
+    [StorableConstructor]
+    private ReferenceParameter(StorableConstructorFlag _) : base(_) { }
+    private ReferenceParameter(ReferenceParameter<T> original, Cloner cloner) : base(original, cloner) { }
+
+    public override IDeepCloneable Clone(Cloner cloner) {
+      return new ReferenceParameter<T>(this, cloner);
+    }
+
+    public void ForceValue(T value) { ReferencedParameter.ForceValue(value); }
+  }
+
+
+  [Item("ReferenceParameter<T,U>", "ValueParameter<T> that forwards to another (referenced) ValueParameter<U>).")]
+  [StorableType("83FEA704-6AED-4D76-B25A-B469E0E9187A")]
+  public sealed class ReferenceParameter<T, U> : ReferenceParameter, IValueParameter<T>
+    where T : class, U
+    where U : class, IItem {
+
+    public new T Value {
+      get => (T)ReferencedParameter.Value;
+      set => ReferencedParameter.Value = value;
+    }
+
+    public new IValueParameter<U> ReferencedParameter { get => (IValueParameter<U>)base.ReferencedParameter; }
+
+    public ReferenceParameter(IValueParameter<U> referencedParameter) : this(referencedParameter.Name, referencedParameter) { }
+    public ReferenceParameter(string name, IValueParameter<U> referencedParameter) : this(name, referencedParameter.Description, referencedParameter) { }
+    public ReferenceParameter(string name, string description, IValueParameter<U> referencedParameter) : base(name, description, referencedParameter, typeof(T)) { }
+
+    [StorableConstructor]
+    private ReferenceParameter(StorableConstructorFlag _) : base(_) { }
+    private ReferenceParameter(ReferenceParameter<T, U> original, Cloner cloner) : base(original, cloner) { }
+
+    public override IDeepCloneable Clone(Cloner cloner) {
+      return new ReferenceParameter<T, U>(this, cloner);
+    }
+
+    public void ForceValue(T value) { ReferencedParameter.ForceValue(value); }
+  }
+}
