Form validation config & dynamic

@silentium: The reason I'd like to do this is because I would like to create a clear structure where everything is set. Thus I thought it'd be better to do it both in config as dynamic. I've got more rules in it, and this is the only part where there's only 1 rule in the holder. The next forms include 5+ validation rules.

I see, then I understand why and agree that @mwhitney's solution would be the best.