That's true, and Swihart, if he converted successfully to 3B, would instantly be second on our depth chart at that position, and the same for first base. It's a question of how much they want Swihart's bat at catcher.
There's definite arguments for moving Swihart to any of 4 different positions that are not catcher, and letting him do his damage with the stick at positions where he'll get more time. Besides the two you mention, he's got corner outfield experience from his college days, so I have little doubt that he can slot in at left field, and only a little more doubt in his ability as a potential right fielder. And there's no reason not to believe his bat would allow him to play the corners either.
THe question pretty much comes down to, how good does Vazquez have to be *offensively* to kick an offense-first catcher out of his position? We think we know that Vazquez will outplay Swihart on D, but considering the verbal commitment to Swihart as the opening day catcher what's the minimum Vazquez has to hit in order to keep himself in the running as a potential starter or even beat Swihart out? Does just obtaining a reasonable OBP get it done? Does there have to be some XBH potential there which Vazquez really hasn't shown yet at any level?