They are permitted so long as you can use them fairly and maturely, same thing with any IC resources, if you can't use them fairly and choose to instead abuse them, don't be surprised when we take away your magic privileges. But they are fairly balanced, as it stands. They are slow, usually require the user to be in weaker armor, and are typically on par or close to other weapons in power. So long as players keep those things in mind and don't go overboard there should be any problems with them,
We never actually used to hold the 'power' or 'energy' of a person's armour in effect for other things like guns or tools before. Are we immediately using how they work with the game's mechanics as a rule for how they work IC?
Not literally, I'd say more as a generalization. Say for example, melee weapons and staves would probably require more dexterity and freedom of movement than a gun would, so you would likely be wearing lighter armour if you wanted to use them effectively. This is not a rule mind you, it's just an idea to help keep them balanced
I don't know about you, but I certainly don't want to walk into a conflict with the giant, expensive, unconsealable staff of bullseye on my face. I mentioned earlier in one of these many new discussion treads, feel free to come up with how the item works. Most of the staves don't actually do things you can't explain through other roleplay routes. If you can't make a sensical way they work or why you have one, chances are you should likely not use it.
That is the other issue, staves would be rare, few people would reasonably have one. And while fun, guns would likely be more effective and less conspicuous. Up to the players to decide on what they want to use though, just remember to do everything in moderation