Yes this question crops up now and again, and the consensus has always been it would not be viable, even if DCE released the schematics.
The only solution is a completely new PPC card built from the ground up, but when asked at Amiwest last year Jens Schönfeld dismissed the idea, so is unlikely to come from Individual computers. The only other small ray of hope I see, is if you listen to the speech Trevor Dickinson made at Amiwest this year, from 32 minutes into he mentions that three new hardware contracts have been signed with Varisys, so some wild speculation on my part, but at least one of these could *potentially* be a new PPC accelerator card aimed at classic Amiga's.
http://www.youtube.com/watch?v=7PdywsoOPmI
We don't really need PPC accelerators for Classic Amiga's. We need new classic Amiga's without the the limitations of the old ones. The old ones are failing day by day and you have to be tech savy to be able to keep one running properly.
I'd want to be able to have a similar speed with a Pentium4 running at 3ghz. I'd want the CPU to be a newly produced - still produced CPU.
I wouldn't care that much if the Amiga needed to emulate 68k.
I'd want to be be able to use "current" industry standards. I mean I don't want to look for ddr2 rams when everybody sells ddr3 rams today. I don't want to look for sata harddrives while ssd on a pci-express is going to become a standard in a year or two. I don't want to look for old ATI cards when I can buy ati 48xx, 58xx and 68xx cards easily today.
This machine should be comparable to PCs of 2005 yet priced around good PC's that are being produced today. 2000$ should be the maximum price without monitor and they should also have a slower version with a 999$ price.