- disabled the scripted virtual function module after finding out that it only works if each single class that may serve as a parent for scripting is explicitly declared.

Needless to say, this is simply too volatile and would require constant active maintenance, not to mention a huge amount of work up front to get going.
It also hid a nasty problem with the Destroy method. Due to the way the garbage collector works, Destroy cannot be exposed to scripts as-is. It may be called from scripts but it may not be overridden from scripts because the garbage collector can call this function after all data needed for calling a scripted override has already been destroyed because if that data is also being collected there is no guarantee that proper order of destruction is observed. So for now Destroy is just a normal native method to scripted classes

src/scripting/vm/vm.h

@@ -667,7 +667,7 @@ public:
 	bool Final = false;				// cannot be overridden
 	bool Unsafe = false;			// Contains references to class fields that are unsafe for psp and item state calls.
 	BYTE ImplicitArgs = 0;	// either 0 for static, 1 for method or 3 for action
-	int VirtualIndex = -1;
+	unsigned VirtualIndex = ~0u;
 	FName Name;
 	TArray<VMValue> DefaultArgs;
 	FString PrintableName;	// so that the VM can print meaningful info if something in this function goes wrong.

src/scripting/vm/vmframe.cpp

@@ -34,15 +34,15 @@
 #include <new>
 #include "dobject.h"
 
-IMPLEMENT_CLASS(VMException, false, false, false, false)
-IMPLEMENT_CLASS(VMFunction, true, true, false, false)
+IMPLEMENT_CLASS(VMException, false, false)
+IMPLEMENT_CLASS(VMFunction, true, true)
 
 IMPLEMENT_POINTERS_START(VMFunction)
 	IMPLEMENT_POINTER(Proto)
 IMPLEMENT_POINTERS_END
 
-IMPLEMENT_CLASS(VMScriptFunction, false, false, false, false)
-IMPLEMENT_CLASS(VMNativeFunction, false, false, false, false)
+IMPLEMENT_CLASS(VMScriptFunction, false, false)
+IMPLEMENT_CLASS(VMNativeFunction, false, false)
 
 VMScriptFunction::VMScriptFunction(FName name)
 {