I think you missed the point there, he was saying it would be possible to make Wup aware of a new card. The AmiJoe was meant to be working, but shelved as it was uneconomical to produce, it'd certainly be a more realistic to make that than re-create the original PPC designs.
Of course none of this is going to happen as there just isn't a market for a classic accellerator any more - not with 2 new PPC platforms already in existance. Perhaps making a hardware AGA emulator on a PCI card would be a more realistic taget? (could be built into the Catweasel Mk36 :-D).