>>48554838I think it's great. Every major trainer should have some ace Pokemon that they rely on.
If I happen to raise a Pokemon that is also the signature Pokemon of another boss then I think that's all the better: mine can go toe to toe with theirs, hopefully. I can't remember any specific examples of this though other than maybe my Gallade going up against Lucian's Gallade.
>>48554882It's hard to say what Blue's ace is, since as a rival it's always gonna be the starter that beats yours, and as a regular boss they make sure it's pretty even.
For this reason I would want to consider Arcanine, Gyarados, and Exeggutor all his ace Pokemon, but it's probably cheating to consider three ace Pokemon for a single trainer.
I know he's only used it like twice, maybe three times (FRLG and HGSS rematches, possible in Battle Tree) but maybe they should start associating Tyranitar with him, mostly because I don't think Tyranitar is associated with any major Gym Leader or boss fight as far as I know, unless I missed someone.
Plus it's a strong Pokemon, and is found right near where Red is in the Gen II games. Maybe this is a stretch.