Trek in most all its forms has had cameos. Especially TNG... seemed everyone wanted to play an alien in TNG. On my visits to the set, I met a couple of those people.I don't see how a delusional bigoted actor who wants to save the world by making it all scientology would be good for star trek
He is--or at least was--an enormous box-office draw. Irrespective of what people think of him personally, having a "major" star in Star trek in any capacity would help make it look new and different from the stogy old Trek that died from terminal uncool.