Based on the way the Browns have handled this offseason, LT being their number one goal in the draft is a given. Now if something changes -- like they trade for Williams -- then perhaps perhaps not. Otherwise, drafting a blue chip LT is going to be Priority 1A.
The thing is...we fans don't know how the Browns have rated this crop of tackles in terms of their ability to play LT. We know what the pool of guys in consideration for that may be, but how Berry/Callahan see them may be quite different. For example, suppose they see only 2 blue chip LT's in this draft, one goes off the board at 4, and they think there's a good shot Arizona takes one at 8, leaving us out in the cold.
I agree that analytics generally argue against trading up. On the other hand...we don't have a left tackle, and the odds on us being able to pick up a blue-chipper down the road are slim. This may be the best shot we have in the next 5 years to get one. So I wouldn't be shocked to see a trade up, because I think it is that critical a need, and this is an opportunity that may not present itself again for a long time.
I suppose an alternative route may be that if the LT's are going off the board, the Browns may do a last-minute trade for Williams rather than burning assets to trade up. They'll then draft a second-tier LT and hope to coach him up. But Williams could be gone by then, or the asking price may be too high considering his demand for a new contract.