heihachi and ryu represent two different genres of fighters but it's debatable whether or not that distinguishing factor matters all that much when smash is firmly a 2d game
i think he carries more mascot power and distinguishing features than lloyd, which is more important. tekken is an internationally renowned series and tekken 3 was one of the defining games of the 5th generation, but it's not really a nintendo game. lloyd represents tales of symphonia, which is beloved but not necessarily smash-material popular nor is he a psudeo-nintendo character like bayonetta, geno or kosmos
heihachi is also way more unique among the roster- there's only one other traditional fighter, ryu, and heihachi is way more brutal. he also has a built in wavedash! the current smash roster already has a lot of nimble bishounen swordfighters, so lloyd wouldn't stick out very much.