Let's try this again.
In terms of newcomers you want in a Smash Bros. game, which ones you want could be easy to master and which ones do you imagine to be hard to master? In fact, which characters you wanted that got in did you think were easy to master, or hard to master for that matter?
I'm still amazed by how randomly technical they made Banjo-Kazooie. You'd expect them to be a classic bing bing wahoo character and instead I had to fully master B reversing and aerial grabbing just to be able to use their down special effectively.
Then I learned all the down throw timings, the ideal spacing for their tilts and how to snap to the ledge with Wonderwing. Had to learn what 2-framing even is. Finally, mastered Breegull Blaster and its combos like three years in (it becomes their best move at that point and now I use it too much!). Still missing the KFC stuff though, and I'll probably always will.
All that work just to be able to stay in the game. I think the way they ask so much out of you turned a lot of people away from the character, I believe they're super fun and expressive once you've learned all that stuff, but I wouldn't mind it if they were to simplify them a bit for the next game. Would've given up much earlier if I wasn't a super fan.
Pac-man is similar, he has such a friendly appearance and then you have to learn 75489 different techniques with the fruit and the hydrant. Gave up with him, though I love the way he's designed.
As for newcomers, who knows how they'd design them, I don't think the source material influences much how easy or not that easy a character is to play as, but if Dark Souls ever gets a character he'd have to be difficult, right?