The precedent has already been set for this by the Clerics' 'Follower of.....' line, each of which specializes in one specific weapon. This line also introduced the idea of automatically granting a 'feat' with the enhancement, since the line you choose also gives you a bonus weapon profficiency. So including the ability to make Qstaffs finessable when you choose Way of the Acrobat certainly wouldn't stray from DDO's development philosophies.
I keep seeing people claiming that making Qstaffs finessable would be unbalanced. Can someone please explain to me how it would be overpowered as compared to normal two-hand weapons on a high strength character?