using System.Reflection in Custom Editor for flexible tool (somewhat long)

I'm attempting to create a custom editor that allows for multiple behaviors to be attached to an object in the editor.

The goal of the tool: I'd like to be able to create subclasses that derive from a base class that can be assigned into a custom script I've written.

The goal of the inspector: I'd like to be able to automatically detect available subclasses and offer them as selections to be added, without having to write new code each time a new subclass is written.

The code I've got so far: please note, this is my first foray both into System.Reflection and also Custom Editors, so please point out if I'm just barking up the wrong tree entirely, or flat out doing things wrong. Thanks in advance!

Editor Class:

 using UnityEngine;
 using UnityEditor;
 using System.Collections;
 
 [CustomEditor (typeof(Container))]
 public class ContainerEditor: Editor
 {
     private SerializedObject obj;
 
     public void OnEnable()
     {
         obj = new SerializedObject(target);
     }
 
     public override void OnInspectorGUI()
     {
         foreach (var item in SubclassFinder.FindDerivedTypes<ReturnBehavior>(null)) //this works if I only return the names of classes. if I can somehow return a reference or create a way to instantiate a class from here, that would be ideal
             GUILayout.Label(item.ToString(), EditorStyles.miniBoldLabel);
     }
 }

container class:

 public class Container : MonoBehaviour 
 {
 
 
     public FunBehaviors[] funBehaviors;
     
     void Start () 
     {
         
     }
     
     void Update () 
     {
     
     }
 }

base FunBehavior class:

             public class FunBehavior 
             {
                 public Container container;
                 public FunBehavior ()
                 {
                     //CONTAINER OF FUN
                 }
             }

   

 
 

child class #1

 public class SooperOssmFun: FunBehavior 
     {
     
         public SooperOssmFun(Container c)
         {
             //OMG ALL TEH FUNTIEMZ
                 container = c;
         }
     }

child class #2

 public class MegaOssmFun: FunBehavior 
         {
         
             public MegaOssmFun(Container c)
             {
                 //NO SRSLY LIEK WOAH FUNTIEMZ
                         container = c;
             }
         }

static class to return classes to be displayed in inspector and later added to the container script on Editor controls.

 using System;
 using System.Reflection;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 
 
  public static class SubclassFinder
     {
         public static IEnumerable<T> FindDerivedTypes<T>(params object[] args) where T: class
         {
             List<T> objects = new List<T>();
             foreach (Type type in Assembly.GetAssembly(typeof(T)).GetTypes().Where(t => t.IsClass && !t.IsAbstract && t.IsSubclassOf(typeof(T))))
             {
                 objects.Add(Activator.CreateInstance(type, args) as T);
             }
     
             return objects;
                                                   
         }
     }