Real talk we need to be more into the idea of double-dipping. Beyond the fact that the SMT and Persona fanbases are completely different (and it's a known fact), even if they were the same, this bull**** of "you already got your thing, shut up now" needs to go away.
Like, if Cloud had gotten in last FP, and people were asking for, say, Sephiroth now, that's not selfish, that's wanting to make the game even better. More representation for iconic games isn't a bad thing. And the notion of a fanbase getting too pandered to, well, I can get the unfairness aspect, but the way I see it, we're pretty far from any franchise starting to be perceived as pandered to (only one I can think of is Metroid, because it got two newcomers in base so one for DLC could be seen as overkill).
Even then, is it really that big an offense to take people to task over them? If DQ fans want another character (say, a villain, or one of the iconic party members), is that really so bad? If Banjo fans have switched to asking for Grunty (or Conker, or freaking Joanna Dark, I dunno), or if SNK fans want Kyo or the Metal Slug crew, what's wrong with that? (Pretty ironic given that the person calling SMT fans selfish does indeed want the Metal Slug playable.) If it happens, criticize the game, criticize Nintendo and Sakurai for what you perceive as a bad design decision, that's fair, but why do fans have to answer for their tastes?