Do you refer to the flattened source file, containing all inherited contracts? We do generate that information, since it's what's used to verify on Etherscan (by running$ oz verify), but I'm not sure if we actually expose it as an artifact. @jcarpanelli?
Absolutely! We wrote a guide for doing this using the Gnosis Multisig, but the process to have your own contract be the upgrade admin is not too different.
@ylv-io participated on a Moscow podcast and workshops a couple weeks ago, he's probably the person to talk to.