Yeah sure if you're a few years away from moving them but the techniques are different, and in this discussion at least, we're talking about cutting Fisher next year. So now they've spent their first year not working at tackle. Add to that you still don't know how they'd look on the outside when you get to the next offseason, so do you need to draft another tackle the next year or not? You may have no idea because they don't even have practice reps to review.
Not that it can't be done. Anything is an upgrade over our last swing tackle.