You might want to try out self hosting hydra! It's pretty sweet for your usecase (building and caching Nix stuff, in a smart way). It can even run arbitrary commands (e.g. moving a release branch)
EDIT: here's how I do it, in case it's useful: https://github.com/Misterio77/nix-config/blob/a74b2ede/hosts...
Weird the author said email was a pain, but last patch I received it was as easy as `himalaya read --raw X | git am` to apply & pointing out that modern email clients do a bad job supporting this seems more damning of those clients than the workflow.