Simmons if he is there, because you just can't match his skill set in free agency. All the young, fast ILB that can cover TE's are not going to become available. I also think about what our defense was able to do when we had a dangerous blitzer up the middle with DWash.
Okudah is 2nd "can't pass" because he has the tools to be an elite CB, and we might very well have a need next season if Pat P leaves. Its a big money position that is not impossible to fill...but it would be pretty awesome to have a CB#1 on a rookie deal for 5 years. It might even allow us to resign PP21 if he's willing and transition him to a potentially elite FS in his 30's.
Wills and Brown are then next for me. I would be ok with either one.
After that it's a trade down to acquire more picks, and then I'm ok with pretty much anyone.