I’m not entirely sure what you mean by userbase, but based on your description it sounds like you could set up a Wordpress docker container with some plugins to handle what you want and then use the Wordpress api for the calls. If you’re looking for like a paid membership situation for the site, there are free and pay plugins that can accomplish the payments and subscription integrations.
This is exactly how I have mine set up and I really like it.
I’ve got an internal and external domain with a wildcard cert so if it’s a local only service I can easily create a newservice.localurl.com, and if it’s external I can just as easily set up newservice.externalurl.com