So you were put in charge of making the 060 based amiga

[Zac67]

Big box:

Dump Zorro, PCI only. 5 slots minimum. If it's very low additional cost include 1 or 2 Zorro slots.

SCSI was somewhat expensive, make it optional. EIDE (MW-DMA!) as standard.

Separate CPU & RAM card, no RAM on mainboard. Memory map allows up to 1 GB of RAM on the CPU board.

Move graphics chipset to PCI/Zorro card to make it optional later on.

[Zac67]

I would avoid the EC models and offer fully functional CPUs that can handle the ZorroIII bus that you also want to have available.

What have the EC variants got to do with Zorro III?
A 68EC020 lacks the 32 bit address bus, but '030+ shouldn't have any problems.