Rather than spending a lot of time discussing potential hardware, I wouldn't mind focusing on what's here or close to here.
Exactly my approach. There is a saying in German: That's unlaid eggs.
Use what's there or very close. In case of MorphOS that is Pegasos 1&2, Efika 5200B, Mac mini G4, eMac G4 1.25 GHz and, close (probably late August/early September), several PowerMac G4.
PowerMac g5 and Powerbook are both nothing to expect too soon - worked on, but unlaid eggs.