Joker, Hero, and Banjo already made it worth it for me.
Well, considering that Project x Zone is an Action-based RPG series, it makes sense that Phoenix Wright wasn't in it..I mean, they had to make-up a reason for him to be able to do anything other than just being there..Phoenix and Maya are not fighters at all..they literally only got included in PxZ2 because Ace Attorney is a popular series.
Though, yes, along with Street Fighter, Monster Hunter, and Mega Man, Resident Evil is one of Capcom's most prolific, popular, and profitable series.
I don't know if Capcom were the ones to decide that Chris & Jill were the 'headlining' units in Project x Zone, I mean, Namco and Monolith were the ones that made it and just licensed the characters from Capcom, Sega, and Nintendo/Intelligent Systems.
From a storyline standpoint though, Chris and Jill make sense since they are from a Government Organization like the other main characters of the series itself are.
Its possible that Nintendo just did that because of Resident Evil being a big series and likely brings both them and Capcom a lot of money while the Dragon Quest series is HUGE in Japan, so of course they'd spend a lot of time on it and are likely, once again, hoping to improve the series popularity in the West to bring both them and Square-Enix more money.
I doubt either had a lot to do with Smash Bros. at all outside of Nintendo showing a Dragon Quest XI S trailer immediately after the Hero's reveal.