Google don't quite directly support this, but the multi-user support and account switching are actually quite good and robust. My understanding is that multiple accounts have effectively no correspondence -- your individual accounts do not trust one another, which makes a lot of sense.
You still don't transparently switch modes in different spaces, but you can supply that.
The "change my ID by space" model, along with a non-advertising revenue plan, is Imzy. Actually, they take this one step further, in that you can opt to be anonymous (with a freshly-created, random username) in any given post (if allowed within the community). That and some other features are interesting.
The actual experience leaves a great deal to be desired, in my experience. On-demand anonymity like that does lead to a huge potential for abuse, and requires very active moderation. I found myself the subject of unceasing attacks in a thread in which the Imzy CEO and community manager were each prresent, and where the latter denied that there was a problem. One of the community leads finally came in and locked the thread -- a mail glitch had dumped all alerts to her spam folder, and activity in that profile is usually far less than what had appeared (the post is over 60% of all comments to date, over the past several months).
https://www.reddit.com/r/dredmorbius/comments/500ysb/the_imz...