No, always glad when people have questions like this. It means they're actually getting into the game and story, which is great!
I can't say one way or the other whether I'll have more non-Mezz gameplay, It kind of comes down to what presents itself story-wise. I will say I probably won't have FULL gameplay, fighting and all that, because lord would that be a lot of new art assets. But I have full walking sprites sitting around for most of the characters, so if it's something like that, it's always possible. Just depends on how things go.
Scratch will definitely be sticking around, and have some extra stuff as time goes on. I probably won't be introducing any other allies/rivals that kind of thing, but there will obviously be new named characters with each chapter.
Almost certainly just the staff. It's an art asset's thing: I'd have to redraw something like eight battle sprites for each new weapon (and the nude versions, and on and on). Plus the staff is just kind of his thing, it's part of his design and all. The plan with the special moves are that there's a new one for each chapter to keep things interesting, but none of them carry over. Balance would quickly become a nightmare if I had to account for all of them.
Thanks for the questions, and for playing the games!