I think this is a good proposal. As a side note, we've just completed that exercise for the OP-TEE project [1] and in general it seems like most people appreciate the change. One thing where our process differs compared to what you've proposed is that we are still using GitHub for everything and that is connected directly to https://readthedocs.io using webhooks, which has the nifty feature that as soon as a patch (pull request) has been merged at GitHub, readthedocs will automatically be notified (webhooks) and will immediately rebuild the documentation and publish it. I.e., we always have the latest version available and published and there is no extra cost involved in manually having to deploy the "_build/*" stuff. I'm not sure if that is doable with existing TF infrastructure, but I think it's worth investigating whether someone like that is possible to do, since it saves us from doing "unnecessary" work.

[1] https://optee.readthedocs.io/ and https://github.com/OP-TEE/optee_docs/