The idea that we're going to "upgrade" this Oline is a bit of a stretch.
You can't have an All-Pro at every position.
The hardest to find is LOT. Jackson is doing an admirable job against good DEs and OLBs. Why spend the money to get a new one?
But it's not just that. Oline players have to complement one another, and you can't just throw a bunch of guys together. Chemistry
We already have chemistry. Yes, Dotson will be expensive. He's that good. And, he's meant that much to our Oline's performance. Even if we have to lose Witherspoon to keep Dotson, that means losing a middling player for a top 5 at his position player. No contest.
We have 3 inexpensive players on the Oline, even next year. Assuming Jackson gets a 2nd round tender, that's $4.5 mil (for an LOT, that's cheap). Avila, rookie contract. Shelton, inexpensive. Dotson, my guess is $16mil per year. Havs, a bit over $11mil. But you get what you pay for. And what a difference a good Oline makes. And, they'll save $5mil in cap from cutting Allen.