(alpha omega, a relatively high-standing clan on PO as a whole filled with people that know how to battle)
I personally cast my vote for having it be the default tier, if only for the fact that if not, it's going to end up like Clear Skies was- unused. While you could argue that "people who want the tier can use it to show their dedication", you need to remember that not everyone on the server knows what tiers are, and the majority are going to ladder on the default tier, whichever it is. It's already standard elsewhere, even in the games themselves, so why shouldn't we?
tl;dr Wifi OU for standard tier, most points I'd like to make are explained in better detail by Lobos.