For the purposes of a functioning offense, James is closer to Lane Johnson than he is an inexpensive replacement. Even if the goal is to draft a QB in 2020, you better have a solid OL at that time, and your chances of landing a starting RT in RD 2 are relatively low. Put it this way, James (today) is better than Braden Smith, who was good enough to start and hold his own on one of the best OL's in the NFL.
If the plan is QB in 2020, you can keep James and Tunsil and draft Ford or Taylor as a RG with OT versatility (position each played in college), and the OL will have core pieces in place for the QB you draft in 2020. After QB, OL is literally the last group you want to cheap. I mentioned it in another thread, but thinking you can cheap the OL because the Patriots have is like thinking you can cheap CB because the Seahawks did with the LOB. You probably won't be able to replicate their success, and if you fail to do so, your team won't be competitive.
If the plan is QB in 2020, you can keep James and Tunsil and draft Ford or Taylor as a RG with OT versatility (position each played in college), and the OL will have core pieces in place for the QB you draft in 2020. After QB, OL is literally the last group you want to cheap. I mentioned it in another thread, but thinking you can cheap the OL because the Patriots have is like thinking you can cheap CB because the Seahawks did with the LOB. You probably won't be able to replicate their success, and if you fail to do so, your team won't be competitive.