They would have to do them as throwing weapons with two-handed alt-fire mode so that the power throw requirement applies.
If they were able to make alt-fire modes on regular weapons that turned them into throwing weapons, but only worked if you had the PT requirement, that would be pretty awesome. The two handed swords already have alt-fire (polearm mode) but the axes and hammers could be thrown...
Really they could take two approaches to thrown weapons:
Currently, throwing weapons are great for throwing and bad for melee.
Why not have a second set that's great for melee and bad for throwing? Like a weapon that's statistically identical to the Great Axe when used in melee, requires PT 6 but can be thrown? It's kind of like saying "this is just a normal battle axe, but you CAN throw it if you have the skill".
Alternatively I guess they could just allow anyone to throw anything, it's just that with PT 0 and 1 throwing wpf you aren't going to hit anything or do any damage....
ANYway, I really just want one usable throwing weapon that alt-fires into two-handed wpf.
Anything beyond that is just gravy.