An example of why this would be less exploitable than an online Brawl ladder: If someone has two Wiis, they could keep setting up matches against an idle character and gaining rank. With the SWF ladder, you'd only be able to play semi-respected members of the forum (100+ posts or so?) that have been approved. We could also set it up so that not only is each account unique to the SWF user, but also to their Wii ID# and/or IP address.
The PHP
There are a few things i don't like about this paragraph in particular. First, Post count has nothing to do with skill/ respect.
Second, about Wii ID#/ IP address, what about the possibility of having two players to one Wii? I go to college now, and there are plenty of roommates that play, but only have one system (it'd be stupid to have multiples). For instance, My roommate has a Wii, and i do not yet have one. We both play smash though. Also, what about those players who don't own a Wii, but are still competitive? Two guys in my crew in particular don't have cubes (well, ankoku got his very recently), but they played frequently, due to the convenience of a dorm, and other people having the game.
Also, what tier would people start at?
Actually, I'm kind of agaisnt a ladder based on matches set up like that, i'd prefer a ladder based on points for tournament placings (pts based on prize $, attendance, and people attending). But i'm just pointing out a few things that you could make better about your system.
for the record, i don't see brawl's potential network play being used in the competitive setting for performance reasons.