If we're going by requests for a Namco character, then it's a toss up between Heihachi/Jin and Llyod/Yuri. Maybe Kaz too, but I've seen more people talk about Heihachi and Jin than him, either way a Mishima, given requests shouldn't be too out there of a choice. I don't really hear anyone else talk about Namco franchises outside of Tekken and Tales too much since that's what people care about the most. Though obviously, Soul Calibur's also got some support. And Digimon to a lesser extent. But it's not like people are asking for Dig Dug or Klonoa that much.
I'm a bit surprised Digimon's the biggest money maker after Pac-Man though, would've thought it was Tekken. But I wouldn't be opposed to a Digimon, just not my first choice is all. I guess that's mostly because here in the west, Digimon fell off a bit. It's still around but didn't quite get the staying power as Pokemon.
Tekken's the OG for me, so I'd be beyond ecstatic if Jin or Heihachi were added in Smash.