Sadly for $15 - $20 you can buy fast ARM chips with integrated graphics that far outperforms anything that AGA could offer.
Or for $25 - $30 you can get GHz class ARM designs with fast PowerVR based graphics, video acceleration, etc. An NVIDIA Tegra 2 probably won't set you back too much more than this either.
Maybe you could take the Minimig AGA VHDL and compile it into a hard core, and then attach a TG68k or N68050 style CPU into the same ASIC (or fix it to an ARM), and all the other stuff, but it would still cost a lot in terms of up-front design and engineering effort, and if you can afford that, you can afford to get a deal on buying 100k+ ARM SoCs.
Maybe five years ago, maybe even certainly ten years ago (if a single-chip AGA++ had been produced, which would have required Amiga/Commodore to be alive, and all this pie in the sky stuff that's not even worth considering). Not today.
