The example of rays/touch attacks simply illustrates the problem.

If you have any character who is designed to use a particular kind of weapon, and lacking ability to attack with other weapons, this "flaw" isn't all that serious.

Basically, this is a class of flaw/disadvantage that only really hurts if the DM targets it -- if you are in a campaign where you are constantly disarmed, or where you don't get weapons custom-built for characters, this flaw is serious. Otherwise it is really really minor for a heckload of classes and builds.

Lastly, the effect described is already captured by the "weapon focus" feat -- that you are better with one weapon than you are with any other.

I don't like it. :)