Altered Beast is actually one of SEGA's most recognizable IPs in the west. You can also argue that being included in the Genesis Mini is kind of a major cross promotion too, I suppose. So far they have only been adding stuff that has some sort of modern presence either within current game releases or loads of physical merchandise. I am not expecting them to break this trend for better and worse.
I do very, very strongly agree though that a platform set instead of a franchise set would be a fantastic idea. Something like Ristar for example is very commonly requested but how many people want a set with him, Kaiser Greedy, the purple guy that throws snowballs at you and I dunno, the mecha mole boss (okay that would be sick)? Makes more sense to make something like a Genesis set in this case with other commonly requested characters that do not really have the same character potential something like Panzer Dragoon, Virtua Fighter or Bayonetta do. People would lose their minds over a set with Ristar, VectorMan, Sketch Turner and Kid Chameleon in it. I have mentioned this a lot online though so apologies if I told ya already, hah.