Most managers won't do this because if your catcher gets hurt and you replace him with your backup catcher who is currently playing DH, you lose the DH. I suppose that the Sox could carry three catchers on their 25-man roster and rotate them at DH, but that seems unlikely, especially with Jose needing a day off of 1B once a week or so. I think it's more likely that Collins gets dealt.
I'm pretty stoked about his move, even though the Sox didn't really need a catcher. They got a nice bat at a nice price. I'll be even more excited when they sign a #1 or #2 SP.