I must be the only one, but I really think a War Machine spin-off has potential.
Rhodey hasn't been well-developed individually in the MCU, and this would give the chance for that. Movie Rhodey has been established as very pro-military chain of command, whereas comic Rhodey has been a little more gung-ho. A spin-off film would allow for character growth and us to see him become more like his comic counterpart.
And there are good comic stories for them to riff of of, such as Chuck Austen's U.S. War Machine, in which Rhodey and the War Machine armor is enlisted by Nick Fury to fight A.I.M. in a Special Operations unit unbeknowst to Stark. Or a storyline from War Machine's 90's solo series, wherein Rhodes is spurred to action by SHIELD and the UN's inaction during an ethnic conflict in the fictional African country of Imaya. If they used this second storyline, it then opens the door for introducing Black Panther and Wakanda as well.
And as we saw in the coda of Iron Man 2, Fury wants the IM technology involved with Avengers, but not Stark himself. Rhodes is trained in the use of the Iron Man suit, so a sensible storyline connection is already there for a WM spin-off to happen.