I think the lack of demand for SAGA (or whatever advanced AGA people are thinking about) in WinUAE says a lot of the need to do it in the FPGA. By all means give us a mode that make the functionality we already have insanely fast but do we really need new functions?
WinUAE is an emulator of classic amiga systems, so there would be no demand unless there was a system that supported something better than AGA.
There is more likely to be demand for PPC/WarpOS/PCI etc.
Technically you are getting new functions.
1) Insanely fast (new function)
2) More CHIP RAM (new function)
No these aren't new functions. Existing software will just work with these without any changes.
Since you already have these two might as well just add the last bit
3) Allow support for more than 64 colors per sprite....say 32 bit colors per sprite....like you see in RTG
4) Add 3D support
and you have yourself a new spanking SAGA custom chipset.
"might as well" is pushing it, there are many reasons why 3d support won't happen. Lack of space in the FPGA being one of them.
You'll be lucky to get graphics as good as a PS1.