Interesting concept. If opponent has an immaterial weapon or shield, does it still get switched? What if yours is immaterial, can you still target it?
Other than that I think this is a pretty cool card... maybe we'll start seeing daggers and short sword get more use.
Since I have left this game for some time, I forgot there are immaterial permanents.
In this case, I think you won't be able to target your immaterial shield or weapon, but the second phase of the effect (getting opponent's equipment ) does not involve targeting, so this card can help you take down opponent's immaterial permanent.
Suggestion: Weapon to weapon, Shield to shield.
Weapon-shield and vice versa don't seem to be ... what should I call it ... equivalent?
I don't think that would be a good idea. In your case of equivalent exchange, you always need a crappy equipment to make this card beneficial to yourself. In the current version, you can switch weapons / shields according your own needs with greater flexibility ( e.g. give your opponent a weapon while getting a dim. shield from him)