Well, I've made my first kitbash (should be a Predator), and I wondered while modelling the mask if it is possible to add a hardpoint/firepoint to his shouldercannon, make a secondary weapon firing a beam and make it look like it has been fired from the shouldercannon. Best thing would be if it needs to be charged up before shooting (odf ) and while loading it appears a red targeting laser from it's mask. (hardpoint/firepoint thingy?)

Then I wondered if it is possible at all to have a meele unit(wampa) having a secondary weap which fires (not changing the weapon like rifle-pistol)

Would be nice if you could help a n00b modeller out

Any normal unit only ever fires from one location. No exceptions.

A charge effect has no relation to the unit model, its position is based entirely off of the hp_fire of the weaponmodel.

Not sure what you're asking for the second part, but almost every melee unit in the game has a secondary weapon that "fires" something.