I'm looking for this: It's fairly long, starts with Engineer figuring out how the respawner works. He think's it's unholy to make people respawn so he plugs himself out of the system. Medic conspires with him and helps him, and then Engi dies. Actual death of Engi is such shocking news that all battles stop for a time. Soon a new engineer arrives by train. He's later revealed to be Cave Johnson's son (with hints of him auctually being the daughter =/). He gets killed a bajillion times on his first 2fort and it is kinda shocking to respawn all the time. Blu Medic and Red spy are friends, Blu soldier is suspicious of Medic and calls him a nazi, Medic is not though he is a sadist and likes to perform very painful medical operations needlessly. He is needed though, because respawner can't cure diseases. Lot's of stuff going on there.
I believe you are looking for Along Came an Artist: https://docs.google.com/document/d/1O7XVaA6Qf4LklQj0OGRO1BY_4D9eEiYoXxfL_rJn6uA/edit?authkey=COr-zxY&hl=en#
Is it unfinished?
Yup.