Interesting idea, but because Trick Room is quite a common move, having it as an ability would be too much of a gamebreaker and should be banned competitively. Pokemon with a huge offensive stat such as Rampardos and Chandelure would probably rise to the Uber tier if another Pokemon happened to have an ability like this. Maybe there should be an ability which activates the effects of Wonder Room and/or Magic Room, since these moves aren't seen too much. It would certainly make the game more interesting with the swapped defenses and the negation of items.
Boilurn, the Scald Pokemon and the evolved form of Hottle. It can burn the holder by the lightest of touches when it boils. It can boil 3 gallons of water in one minute.