Not quite what you probably want to hear, but if you want to have a classic emulator that will be truly useful, I would suggest taking UAE's chipset emulation and modifying it so that it hooks into OS4's virtualized memory and whatever equivalent of that MOS has. That will let old, harware-banging programs like scala work on the JIT emulators on AmigaOnes and Pegs.
It's not quite what you want to do, but it will be a lot less work than building an emulator from scratch, and it is something that is truly needed.
