You mean something like an FPGA based graphics card that implemented the necessary parts of the Alice and Lisa (for AGA) or Denise and Agnus (for OCS/ECS) to reproduce the Amigas graphics in hardware.
I think that'd probably be harder than doing the MiniMig as you'd effectively be pulling out and exposing the raw interchip interfaces and then trying to put a clean interface over them so that they could be called from the "other" OS over some kind of bus. PCI/PCIe most likely.
