Hi @mackoj,
thanks for the details of what you're trying to achieve. For the naming collisions, I'd echo @lsb’s suggestion of separate modules, and you can set the accessModifier: package in the config file, allowing you to consume both clients in a single file. You'd import both modules, one for each client, and where needed, use the fully qualified name, such as GitHubClient.Client.
Now, for attaching macros, that's not easily doable today, but we're interested in offering this feature. There truly are very useful things that it'd unlock, if the generator can simply include specific macros on specific generated types. We have an issue tracking it here, feel free to chime in there, or we can even provide guidance if you'd be interested in contributing this feature!