I feel like Janssen would hold more value than Cecil.
Cecil for Hanigan
xx for Stewart/Cervelli
Janssen+ for Porcello
And still have a solid bullpen of guys like McGowan, Delabar, Santos, etc.
Cervelli was having a great season at the plate and it was only 61 PA so it'd be dumb to extrapolate him but assuming framing numbers stabilize quicker than hitting stats, extrapolating Cervelli to have Stewart's playing time would put them at a pretty negligible difference (~1 run). He's also a good deal better offensively. The durability is an issue though.
I think you're overestimating how much these guys will cost. Cecil for Hanigan makes a good deal of sense and I don't think the Yankees ask for as much as Santos for Stewart. But then again it's inter-division so they may want more or something.
If you factor in Carruth's stats..
0.5 fWAR + (22.7/9.3) would make him like a 3 win catcher. 2.9 but close enough. Stewart had a ridiculous season framing wise. 22.7 RAA.
Available for 1m would be like 333k per win wouldn't it be? lol