I think there was an attempt made long ago with https://github.com/edolstra/nix-make to use the nix-store as a repository for per-build-artifact packages, however, it has long since been ditched.
AFAIK, the only level of abstraction for nix is a derivation, so you will need to try and decompose your problem into smaller derivations if you want to get more mileage out of them. For a kernel? I’m not sure how far you’ll get, probably not very.