I guess ultimately something that also runs on Boom would be ideal. While my main "classic" amiga is my amithlon box I'd very much like to have it run well on a real amiga too. Loses its appeal a little (to me at least) otherwise. If I wanted to make an AB3d mod that require something resembling modern hardware I dont think Id be using the Doom engine
Wanting it to run well on a real classic also helps with not losing sight of the original plan as well, and helps avoid feature creep.