Flaming, shocking etc. weapon ability. You really require the character to spend a standard action to activate the ability?
The RAW require you to activate the flaming/frost etc. ability to benefit from it. The rules say that the effect don't affect the wielder (and by extension his gear) so you can sheathe a flaming sword and draw it still aflame.
But then with flaming weapons you incur in another problem: it make being invisible almost useless.
The sword is sheathed in flame and flame give off light. Invisibility say: "Items dropped or put down by an invisible creature become visible; items picked up disappear if tucked into the clothing or pouches worn by the creature. Light, however, never becomes invisible, although a source of light can become so (thus, the effect is that of a light with no visible source)."
Sheathing the sword should hide the fire but I am not sure if all GM will agree with that as the sheath is invisible too. The two sentences cited above can be read as meaning that light never become invisible, even if tucked under someone garment.
Then we have the magus and paladin (and probably other classes). They can make a weapon flaming as a swift action. And then they have to spend a standard action to actually benefit from that? That make a weapon ability that is already fairly weak (as plenty of creatures have some kind of energy resistance) even weaker.