I hope they don't go too crazy on Kimbrel. He'd be regressing in the last few years and I'm a little pessimistic about what he will bring to the table not having pitched in the last 9 months. Certainly worth a shot if the money is right, though.
If they just give him a bloated 1 year deal that would be ideal. Re-evaluate his value at the end of the season. He probably is looking for more than a 1 year prove it deal though so I'd be OK with something like a 2 year deal with some kind of option or vesting option incentives for a 3rd year. Committing more than 2 or 3 years on a high priced 31 year old reliever whose control can sometimes be wild. Cubs have the $ so if it takes 2 years to get a deal done you gotta shore up the bullpen now. You can probably get a guy with a cheaper salary via trade but how much in prospects will it cost you where Kimbrel is just money at this point.
Cubs are going to be in a tight spot with Strop after this season too because he will be an UFA. He's making $6.25 mil this year so how many years and $ would they be willing to commit to him or would they be better off using that money to get 2 bullpen arms instead. It's hard to believe it but Strop is actually older than Kimbrel as he turns 34 on the 13th.
Lot of $ coming off the books after this season
https://www.spotrac.com/mlb/chicago-cubs/yearly/payroll/roster/
Hamels: 20 mil
Zobrist: 12.5 mil
Strop: 6.25 mil
Cishek: 6.5 mil
Kintzler: 5 mil
Duensing: 3.5 mil
That's about $54 mil there not counting few lesser contracts I did not include and you have guys who are arbitration eligible like Edwards that could always be non-tendered too. Every day Zobrist is out right now is savings on this year too.