Old thread, but it seems no one ever talked about it again here.
I did set this up to play both UFO and TFTD on my PiStorm A500 today. Took some time to get music etc. working in UFO, as you need many files from different places, which is not fully obvious. But all works very well.
Only issue is that the Amiga mouse pointer is visible all the time, along with the mouse pointer from the game (see far right on the 3rd screenshot).
Sadly, this is really Emu68-only. Even the Vampire is too slow for it (not my statement, but from the person who did the Amiga port).