Myself, I would love to see an ATX form factor board with AGA, 040/060 socket, and Zorro slots. Using a standard ATX power supply too. KS 3.9 on a large single EEPROM, on-board Indivison, USB would also be awesome. No daughter cards or things hanging off other chips - just a nice and clean layout.
Kickstart should be in flash & I'm not convinced about Zorro. It's too slow and the cards are too expensive. I can see that someone with a stack of Zorro cards might see it as a positive, but I'd rather have m.2 and PCIe slots.
Using modern ram so that you can dma from disk and have the cpu fetching while aga is saturating the "chip" bus. If you reimplement AGA then it can also run the blitter at the same time and you may as well support ~4gb of chip ram. i.e. stick 4gb of ram in it and map ram in the areas that aren't needed for I/o cards.
Use a socket and you could start with an FPGA for CPU+AGA and switch to an ASIC later.