What? Locking them out of an Eternity, Fahrenheit, Eagle's Eye or Morning Glory is bad for you?
Sure, you don't play this in every matchup but it stops flying weapon decks and gets round the immaterial nature of morning glory. It's not a bad card and your suggestion makes it way better than deflag.
isnt steal also better then deflag, deflag is good because of its cheapness, this card is uselses if you have more then one in a deck and this card is actually WORSE then deflag, it replaces a weapon with another weapon, flying weapon decks just lose a flying weapon because they use one to get rid of this.
Deflag - pros - its cheap, very cheap. cons - immaterial stuff = sad
steal - pros - medium cost, STEAL the permanent - immaterial stuff = sad
this current version - stops most enemys from playing weapons, cons - they get a weapon, higher cost then deflag
version i suggest - destroys and enemy weapon, cons - they get a weapon in return, higher cost then deflag.