After thinking about this some more, Bo and Vlad are the most obvious but would take a ton of years and dollars.
Semien could be a smart guy to extend. Groshans and Martin aren't too far away but Biggio is looking more like a good utility bench player to me. Infield depth has haunted this team forever. I can't even think of the last time we had good depth there.
Given his soft market last year, a 4 for 70-75 or something like that for Semien could get it done to lock him up through his age 31 to 34 seasons. He'd project to start out as a 4+ WAR player at age 31 but would eventually settle in as a 2-3 WAR guy by the contract's end.
If he continues to play like a Top 10 MVP guy like in 2019 and 2021 in his early 30's and in that case he'd provide plenty of surplus.