Using personality as an argument against a character's inclusion? I dare say this sounds familiar. (don't ask)
Nevertheless, Pac-man not having a very recognizable personality is not going to keep him out, it certainly wasn't enough to prevent R.O.B. from joining Brawl.
As for the whole thing about "Namco isn't getting special treatment", Namco may be helping develop the game, but having Pac-man playable in the game is as equal of a special treatment as Sega and Konami got for their mascots being playable, Sonic and Snake respectively. What "Namco will not be getting special treatment" means is that the company will not be getting a ton of content from various franchises they own. This doesn't necessarily mean they won't get any content in the game.
People want Pac-man in not just because they see potential in him, but because, quite frankly, with his history in the video game industry, he deserves it. He is without a doubt, the only legendary gaming icon left not yet playable in a Smash game. They like the character, they like the original arcade game, but do they care if he doesn't have a consistent and recognizable personality? Doesn't seem to be the case.
And keep in mind, this is all coming from someone who is completely indifferent to Pac-man's inclusion.