I don't think the Cowboys are even considering moving Collins back to LG, at least I hope they don't. It's far harder to find good tackles than it is good Guards and Collins appears ready to become a good/great RT. Also, a large part of good O line play is the teamwork/communication that develops among the linemen, not their individual talent level. All it takes is one misread in shifting blocking assignments to get your QB blown up, ala blitzers given a straight shot at the QB (and we saw several of those last year). What the Dallas O line needs is stability, not massive position change. It wouldn't be fair to the player either. The footwork, hand work, and technique are so different between LG & RT that, if they did move him, he'd have to spend almost all of 2018 're-learning' the position. Plus the new RT would have to work on his communication/teamwork with RG Martin. The disaster that befell Green when he tried to shift back from Guard to Tackle is an example. When he was concentrating on tackle in 2016 he performed well in the two games he replaced Tyron, in 2017 after working at Guard all season, he was a disaster when they shifted him back to tackle. What you would end up with, I think, is another year of reduced line play as the players learn their new positions and the communication that goes with it.

Far better to get a decent FA or draft a developmental 'swing tackle'. There are a few available in FA, not All-Pro/ Pro Bowl players, but guys who can hold their own w help for a couple of games. Dallas also needs to have a plan for the O line when Tyron is out vs when he is in. It seemed to me they expected whomever they put @ LT to play just like Tyron, that is unreasonable.