People are right when they say it won't look right.
The weapon mechanics are completely different.
You'd be throwing a pataka at someone in a really stupid way,
as you can't change the way that a character holds a weapon. Their stance etc.
There is also the issue of skill animations. By using different skins,
it can potentially mess up skill animations and can make the skills undetectable which is an abusable bug.
People were unable to see skill animations which were a big issue for PK.
If I remember correctly, it's the reason that the other skins were removed from barbs
(sword I think, can't remember).
Perhaps we can add more psy skins (we do have 20+ skins for psys. I know because
I just SSd them all for a guide x.x), or make some new ones or find something new or something,
but as for making psys wear other weapon skins, I'd say no.
Unfortunately, that's just how the class is. Other classes can wear other weaps, psy can't.
It might be boring but you should be aware of this when preparing to make a psychic.