Sorry for the late reply - I’ve been busy working on other stuff.
I think your suggestion should work but it’s far from ideal because a user would need to manually patch the Foreman code and modify the installer options.
Shell access is, as far as I know, not possible on cloud instances.
I’m just wondering what the reason behind the extension is, as it’s just a collection of custom functions? Wouldn’t it be possible to add those functions by regular db migrations?