It was sad to see the BoXeR fizzle away without a trace. That Mick Tinker guy must have put a lot of work into it and in the end it didn't get the recognition and sales it deserved.
On the other hand, smaller and less ambitious projects may well have proved more fruitful such as the various USB adaptors, PCI bridges etc.
Judging by your finances and manpower I think you should look at things realistically and build up a buffer of cash and get some sort of team together. The Amiga community is full of genius and zero financial sense and this has to change before we erase ourselves right off the map.
Look at BMW for example, or Mercedes and Porsche. You could say they design some pretty bland and samey cars - they're conservative but underneath excellent. By evolving slowly they have evolved strongly and now BMW are talking of a 60,000 UKP car that can do 200MPH!
I think rather than design a novel motherboard or platform that you have a geek-dream about (Hey I have always dreamt of building a CD32 laptop!) you should find something that all Amiga consumers will want.
But whatever you do, do it to perfection. Like the Picasso IV or Blizzard 1230-IV!
;-)