I have nothing against Aroldis. He does what he does (save games) in spectacular fashion. He also does it at a league-average pace though. I believe he saves games at about 83% which, IIRC is right at league average.
I love to watch him take the mound and experience the thrill that goes through the crowd. That might be tough to replace, but I don't know that it wins any games. On the other hand, I'd say that the remaining relievers could at least approach the 83% mark (especially if you can add another strong bullpen arm).
The hope of making a starter out of AC died last year. Sure, they could probably still try, but they show no inclination this year and even if they do, its gonna take 1.5-2 years to develop him into an effective starter (assuming he can be) - he'd be ready to shine as a starter about the time he hit the open market.
If he's not gonna be a starter he can be replaced. If there's no new money to add a bat then a contract will have to be moved. Chapman has multiple arb years of control remaining. He should have value (especially if they believe they can convert him to starting). Of all the contracts that are (or will be) relatively expensive and could bring a decent return, his is the one I would deal for a bat.
Maybe not necessarily Rasmus, but if I found a guy that could improve the core of the lineup at a near salary-neutral level. Gimme a bat that adds another level of stability to the lineup and I can do with a little less flash in the bullpen.