Dark Souls would be awesome and is a good shout, but I do still hestitate to go all-in on it due to its lack of an immediately obvious candidate. Chosen Undead would probably be the go-to pick since he's the main character, but the lack of a real identity or personality makes me a bit skeptical, the latter is usually a big priority in Smash. Solaire has been brought up a few times, but despite being quite iconic, his overall influence in the game itself is limited, I'd be surprised if a side character is chosen as the sole representative of a franchise. Maybe a boss could do since they're what Dark Souls is really known for, of course the Google Theory turned out to be bunk, but Artorias wasn't a bad idea.
I would still expect it to be Chosen Undead in the end since the playable character always seems to be the priority, but at that point I have to compare him to other Namco reps (as I'm only even more certain on #5 being a Namco rep now that Dante's out), at which point I still feel like Lloyd is easily the safest bet.