Maybe they could let you pick your weapon, and if you pick a weapon for which you have no ability points, pop up a message:
"You have no ability points in that weapon specialization. Are you sure you want to use it?"
[Change ability points] [Change weapon type] [Continue Anyway]
Oh, I see what you're concerned about. Unless something has changed in the beta, the starting weapons don't have usage requirements. I can't remember.. aren't weapon usage requirements based on attributes (strength, dexterity, etc) now?
But, yeah, it would make sense to want to move points over if needed. At the very least it should pop up with a warning or reminder.
"You have changed your starting weapon! Don't forget to modify your blah blah..".
