It is really hard to stop alts from being a thing, in any game or website. There's always ways to get past it.
I don't think that this is really a good idea. Beyond the alt abuse dilemma, there aren't many things in this game that would make a good 'reward', unless there was to be some overhaul of the torishop adding, taking away, and editing certain items to accommodate for a bunch of people running around wearing the same rewarded Beetle Force.
I think that, possibly in the future, this could be a possible thing. It's pretty cool to imagine a bunch more colors ingame, and a reward system based on certain milestones (not login rewards, though, that's just a bad idea all around imo). But with how the game and market is now, it just doesn't seem fitting.