To be honest ZAP is not designed to be run as a centralized long running multi user service.
We have talked about implementing "ZAP as a Service" and for that we were thinking of launching a new ZAP instance per user rather than try to re-architect the ZAP code base, which would be a major undertaking.
Having said that the ZAP HUD should work fine when you connect to a remote ZAP instance, as long as you have the right configuration.
Can you explain what is and what is not working for you?
Ie can you successfully proxy your browser through the remote ZAP instance?
In what way doies the HUD no work? Does it not appear or ??
Cheers,
Simon