I currently don't have time to read the whole thread but if you're serious about this then you should try to get the AAA design. There was much stuff already done, and this would make a lot of democoders happy. I'm not into electronics at all but he design of the AAAchipset could be used on a PCI card from what I recall from old discussions about this. The demoscene and retro lovers alone would be the only market for it in my opinion. Maybe some other very little niche stuff... The Amiga's copper is unique and would allow stuff like dgraggable screens. Maybe some future AOS4, MOS users want that feature. Maybe there are also very interesting gfx effects that are more easily achieved with the Amiga chipset also...
By the way, I think AAA was to be compatible with ECS only and not AGA, but after all time that has passed so many demos use AGA and coders learned to bang AGA directly that I think it should be AGA compatible.
Best of luck to you, if you're serious you'll have a hard time.
By the way, let me also suggest that you don't give up important stuff in your life to do this, I've done similar things and it's stuuuupiddd......do it in part time just for the pleasure, and we'll talk in ten years... :-D Unless you can convince Dave Haynie to help you... 8-)
