@Chucky:
If you were to implement the integer CPU, an FPU, an MMU, and the chipset, in which order would you tackle those?
First CPU and MMU - the MMU is the uttermost important, now you can already attract an audience and developers far beyond the Amiga realms.
Then FPU.
Make sure this runs really well, and gets tested and used with a range of operating systems and hardware. Not just Amiga.
Amiga chipset is already implemented several times, so I would initially just use what exists, Minimig AGA. Other platforms use their chipsets, or implement them on FPGA as well.
Then have the "Amiga team" extend and improve AGA core, and the "CPU core" team add extra features to CPU, FPU, MMU, whatever, _in communication and agreement_ with core developers of all the involved 68k platforms.
Well - this is how I would have done it.