Hat tip to Jonathan Boraz for helping me to hash this out this morning. I think we've figured out what the Rapids are doing. A bit complex so stay with me.
Doyle is signed through 2017 with an option for 2018 at just under $1.2M a year with no transfer fee.
Teams get $800K in TAM in 2016 and again in 2017.
If a team uses TAM to buy down a DP they are then required to sign another DP of higher value.
So I think the Rapids are using TAM to buy Doyle down to the ~$400K max salary level so he's no longer a DP. Then they sign Howard as the replacement DP.
That leaves the Rapids with 2/3 DPs (Howard, Gashi, and Ramirez if he returns) and a bunch of GAM to use. If Ramirez doesn't return we can still sign a DP and regardless we can sign an above-salary player (or two) and use the GAM to buy them down to max salary levels.
Of course this makes it really hard to sign many other players in the $200K-$400K range due to the salary cap. We'll have 3-5 max salary players and a bunch of sub-$200K players.
The one twist in this is that we've been acquiring TAM when we would theoretically have enough to buy Doyle down without needing anymore. so that could mean we plan to sign somebody with the additional TAM or we want to buy down Gashi or Ramirez (if he returns) instead of Doyle. I think the general idea is right though. One of Doyle or Gashi (or possibly Ramirez) is being bought down with TAM with Howard as his replacement.