I just tried the mac driver in MAME again since ages and it runs System 7 quite well.

One issue I'm having is the "proportional" positioning of the mouse pointer in the emulated machine in reference to the mouse on my real machine. Is there any way to have the emulated mouse just get set at the same position as the host machine and, whenever it is out of bounds of the emulation window it freezes at the point of exit, like in VMWare Fusion or Parallels Desktop?