My main interest is my Amithlon box, so I guess OS3.x. I would like it to work on my a1200 too, but amithlon is my main used computer here, so its a priority.
Maybe I'll just fix PRBoom and add freelook to it. That'll cover amithlon/aros, and if NovaCoder adds freelook to Boom that'll cover the classics.
Really though its not just because Boom isnt RTG friendly that Ive considered porting another engine. It's all about the AB3d:TC and what suits that best.
Unless you are going to emulate the fancy texture and lighting effects, I believe we can squeeze enough out of plain old BOOM to create feature rich maps that contain enough mapping and game play elements to make it look and feel pretty much like Alien Breed, as well add in enough BOOM specific tricks to make it feel some what like a successor of sorts.
Of course if life were kind, GzDOOM would be more portable, then we could FULLY engorge our selves, but that is a Windows and Linux only venture as things stand. And beside it requires a modern gen graphics card to fully utilize all it's features, but man can GzDOOM impress!!!