AZ Phil on the Cotton acquisition:
Back when he was healthy, Cotton featured a swing & miss plus-screwball, a CT FB that sat 92-94 T 95-96, a SL, and a CV, so he has the full array of pitches needed to be a starting pitcher (again... - IF - healthy).
Cotton does have two minor league options left so the Cubs can stash him at AAA Iowa and (if healthy) he could ride the Iowa - Chicago shuttle in 2020, but because he has accrued more than three seasons of MLB Service Time, he has Article XX-D rights, which means he can elect free-agency if he were to be outrighted to the minors.
And because he has spent so much time on the A's MLB DL/IL over the past couple of seasons (two full seasons worth of MLB DL/IL time) Cotton is eligible for salary arbitration (which is probably why he got DFA'd by the A's), so he is a possible non-tender candidate on 12/2, especially if the Cubs don't want to risk going to arbitration with him if he and the club can't agree on a 2020 contract.
Keep in mind that a contract awarded via arbitration (by rule) could not include a minor league split salary or performance bonuses, both of which may be a deal-breaker for the Cubs if they suspect Cotton will likely spend at least part of the 2020 season at AAA. It's very possible that given Cotton's recent injury history, the Cubs would prefer to pay him a low MLB base salary (like the MLB minimum) but with easily-achievable performance bonuses if Cotton proves to be healthy and able to pitch in MLB in 2020, together with a minor league split salary (probably somewhere around $250K) if he is optioned to AAA and spends at least part of the 2020 season at Iowa.
So the Cubs have about a week to work out something with Cotton if they are averse to possibly going to arbitration with him and potentially getting stuck with a contract they don't like.