When Inklings were confirmed for Smash I tended to reeeally overthink how their moveset would play out. I figured they'd be all about zoning and territory control, using every one of their weapons in Mega Man-like fashion. I wouldn't peg them for physical fighters. They come out, and they're a very fast, physical fighter who's gimmick is tacking on damage multipliers.
When Joker was confirmed for Smash I also overthought his design by a lot. I figured he'd be using his Wild Card ability to cycle through Personas to use different spells. Instead he's a sneaky, fast fighter who gets a temporary buff by summoning Arsene.
Even leading up to Terry, I remember going so far as to speculate that a potential route with SNK in Character Pack 4 could be a three-in-one character to represent SNK's signature KoF team setup, but instead they just settled with doing Terry, with Fatal Fury as his franchise.
I guess the point I'm getting at here is I'm not going to overthink how an ARMS character will play. I think they'll be a mid-ranged fighter with close-ranged burst options, that their gimmick will be charging their ARMS (+ potential Rush Gauge) and that their special will be employing only the repped character's default ARMS in some unique fashion. For instance, as an Up-B, if you take Lola Pop, she could use Funchuks to spin them around and create a helicopter effect, or Min Min could shoot a straight laser down with her Dragon that gives her horizontal movement but not much vertical. Maybe their FSmash attacks could be a rekka, because it'll most likely be a standard extended punch and you can do two at once.