@bloodline:
UAE is an software emulation. And software just won't get it cycle exact to realtime. And for some applications software emulation won't cut it.
@mikej:
As for 68000 softcore, someone mentioned a successfull run at 27 MHz. Maybe we can go higher with optimization.
I agree with mikej that expandability is desireable. However I think the real point is that of ral-clan "We desperately need fresh, healthy new Amiga clone hardware, soon.". And this re-implementation should occour before hardware to replicate is all non functional.
The second goal should be to eliminate any dependency of companies or persons that goes out of business etc.. A tarball of HDL sources won't "die" like physical hardware can.