There is a gpg program config key for Git[0], but beyond that I am not sure what else would need to be done. I am sure a blog post describing your experience would be well-received.
I tried a bit (i'm only using gpg for my pass keyring, but as pass is dead simple i wanted to write a clone and hack around sequoia), but i found the command-line interface to be missing some features. As a showstopper it doesn't seem to allow on-the-fly decryption of secret keys to sign/encrypt stuff (at least i didn't get it to work). Also, there are very few options for editing secret keys (subkeys, managing certifications). Keyrings are amusingly barebone: they are just concatenated keys (as armored ascii), seems to do the job.
I'm confident this will improve in the matter of a handful of months tho. I didn't check but i'd bet this is mostly a problem of writing the front-end cli code to advertise all the library features. They seem to be pretty active, 1.0 on the lib was cut not so long ago and 'sq' (the executable) is still pre 1.0. Other execs are sqv (verifier) and sqop ("stateless command interface", seems to be oriented at scripting, apparently aiming to drive interop between implementations).
