Just watch as Spring Man turns out to be the Smash fighter pick and the Assist Trophy is replaced by Springtron.
It's an interesting opportunity to set him aside as the presumptive lead, though. But his position as the cover character has always been shared with Ribbon Girl from the start, and there isn't that much in Arms itself to solidify Spring Man as the default or lead character anyway (apart from Springtron being modelled after him). What Spring Man's design does accomplish, though, is encapsulate the concept of the whole game in a succinct way. You see the idea of extending/retracting baked into the aesthetics of springs in a way that isn't quite so inherent to the other materials (mummy wraps, snakes, ribbons, noodles, braids, and so on).
I'm personally hoping for the pick to be Min Min, who was the closest thing to my main-main from day one, and would objectively be well justified. But that may be as influenced by wishful thinking as hoping for Edelgard over Byleth not so long ago.
Arms on the whole has arguably the best, most detailed character animation in any Nintendo game. I spent a lot of time in the game clipping replays and taking screenshots just to savour everything that was going on.
C'mon he's not that bad.
The problem with the game is motion controls (not to me, but for many people).
Played it 100% with motion controls since day one (I tried the controller scheme in the pre-release demos and decided I'd rather learn it with motion). Definitely not for everyone, but a
very satisfying experience to master for those who are willing to grapple with it and get over the hump. But I'm the one always stumping for Skyward Sword and Star Fox Zero, and wanting a more nuanced successor to Wii Boxing was what interested me about Arms in the first place.
I honestly enjoy Arms multiplayer more than Smash. Relative to most other fighting games it takes the emphasis off the inputs and puts them substantially on the situational/spatial awareness and high-level strategy. That's never going to appeal to people who would, justifiably, rather pursue games with a high skill ceiling on technical precision—but what Arms lets you do is experience the opponent-reading/metagame aspects of a fighting game without treating the inputs themselves as a hard prerequisite. You would think this puts it at risk of being a "casual" game with a skill ceiling that you hit too quickly, but there is enough moment-to-moment tactical interest and depth to the loadout metagame to make the game sufficiently deep.
That said, the top end of the ladder
does play more or less Pro Controller-only, and last I checked, the gloves that came with Max Brass are heavily favoured there precisely because they don't have any auto-tracking and therefore reward more precise mastery of the aiming controls. I just personally find it more satisfying to play with motion all the way.