I don't think that many has been done before
Quick correction here on account of
Abra. Technically we've had folks with an entire troupe at their backs (or where their face should be?), not to mention the characters with wealthy benefactors and arms providers, which are probably too numerous to name at this point.
So you may not be the first to try something like that Kamiroo, and you probably won't be the last either.
But just a word of caution for anyone looking to attempt this sort of thing- know what you're getting yourself (and others, such as opponents or clanmates) into when you're pulling characters out of a hat like that. A group full of characters might sound like a lot of fun- and it certainly can be, but it's a headache for sure. So if you are going for that sort of dynamic, I would say be prepared to explain why that extra pack of characters are
worth the headache should you decide to enter into a battle or a clan. The same could be said for intricate powers and backstories however, so it's possible that there's a balance to consider in respect to sheer content and critical details.
But ultimately, so long as you and whoever you end up working with know what needs to be done and are committed to doing it- you'll do just fine.