That's true. They actually stopped supporting Nginx recently which really bothered me too because I want to keep using self-signed certs (my server is only reachable internally and I do not want to expose it to the internet). And the new server they use (I forgot which) didn't really have that option. So right now I'm locked out from updating until I fix that.
And yes it is totally feasible to use upstream! Not a problem at all.
I would recommend to use the dockers though, as the whole debian thing becomes a bit of a mess with different python requirements for some of the bridges. I tried that in a long forgotten past and there is a reason I'm trying to forget that 🤭
Like you I know the ansible playbook has its limits (for example one other thing I run into is that I want to run several instances of the same bridge to bridge eg. 2 whatsapp accounts!) but I do think docker is the way to go. I'm interested to hear how you're faring though as it's a long time ago since I tried that.