I think you're overestimating Vazquez' offensive skills. 200 points, which I assume you mean OPS? Last year Leon was one of the worst hitters in MLB last year. For all players with 200 or more plate appearances, he did have the 2nd worst OPS. But Vazquez was the 7th worst. Leon did have the lower LD%, but it was uncharacteristically low, and typically both players are around 24-26%. Both also typically have the same hard it %. As hitters, they are typically more equal than many seem to realize. The two are the same player.
Why not actually give Swihart a chance? The Sox have had ample opportunities to trade him, and so far, DD has been reluctanct, probably becuase no one will give him anything. As a backup catcher, he might play 30 games a year, which is more than he will play as 3rd supersub off the bench. We've seen he can throw. His game calling and pitch framing probably need some work, but that goes for a lot of catchers.
And right now the Sox bullpen is Barnes, Brasier, Hembree and 4 question marks. That's not a small hole we are talking about. The bullpen will pitch 600 innings a year, and those three might handle 180. That leaves 420 undetermined innings, with roles determined by the personnel we have. And 420 bullpen innings is more important than the 150-250 at-bats from the catcher spot you are worried about. (Yes the new reliever(s) won't have all 420, but there is a trickle down effect in their roles.)..