I don't agree with the idea of locking people out of crafts.
I would however like an extra tier of progression beyond level cap that encourages specialization.. Not necessarily locking someone out of mastering multiple professions, merely time and resource intensive enough to be prohibitive in the same way a PvE player is bottlenecked by Coil lockouts and tome farming.
I'd also like a system that didn't so heavily push players toward diversifying in the first place. Part of the reason there's so many "I do everything" crafters is because you're not gonna be a very good level 50 DoH until you're level 50 in two or three professions other than the one you want to play (unless you happen to really like one of those 'must have' disciplines I guess).
