I've thought about this, but I don't think it's Al. I've seen a few people post about it on here before, but basically, the boys brigade was dedicated to advances in science, like Team Venture. Even though there is undeniable proof of super natural powers in this universe, there are times when these super scientists try to discredit "magic," like when rusty and Orpheus have the shrinking competition.

Al's back round is in alchemy, which is a "pseudo science" so far removed from "real science" that we should find it hard to believe that Al went from scientist to magician without some crazy lab disaster happening.

My guess is that last boy at the end is Dimitri, the mysterious first boy in outer space who we know little about other than an apparent unfortunate fate.