I agree to an extent, but it’s not like there’s just a line of offensive linemen waiting to hop in and start at right tackle on the roster at the moment. And I never really like say “oh we have great coaching, we can plug anyone in and they’ll be fine.” Vollmer has elite size and despite some injury history he is still in his prime, and is involved in every offensive play, while WRs and CBs are not.
That said, it wouldn’t be too much to pick up another right tackle in free agency and draft one, but they don’t have a lot of picks this year, so do you want to add another need? And you’d also have to find a new back-up left tackle, so his departure would open up a couple needs, and most people seem to think the best back-up tackle we have (Marcus Cannon) is more suited for guard.
I could see it go either way if someone’s willing to make Vollmer a big offer, the Pats will not overextend themselves for a right tackle. But I think the safest bet is to bring him back and keep Brady’s protection air tight for his twilight years.