@skurk
Maybe I'm unable to see some major show stoppers ahead...?
There will be problems with anything that peeks and pokes the window and screen structure (which is perfectly legal in most cases). Also, on amiga the windows are rendered to the screen bitmap, if you detach the window from the screen (that will certainly happen here), problems will arise.
The interaction between the emulated and native UI will be tricky to get right.
The same problems arise for anything that has the structures exposed to the application programmer: Any changes on the native side must be relayed to the structure, and any (legal) change to the structure inside the emulation must reflected to the native resource. You will have headaches here.
It might work with some simple apps however.
