I created Threshold Alert and Open Reminder [4.0.0.0;4.9.9.9] for that use case. When configured it will call a rule when and Item remains in a given state for a given amount of time. It has a lot of other bells and whistles (do not distrub periods, initial alerting event, still alerting after a configured time, no longer alerting, repeating the alert if it remains in the alerting state) but that’s the basics of it. I use it to get alerts when a door is open too long, control smart plugs connected to dumb humidifiers, alert when a sensor stops reporting, etc.
Sounds like a good candidate for a library.
It depends on the repo and for add-ons whether there’s an active maintainer for that add-on I think. also, HA has employees, OH doesn’t. You can go faster when you have someone who is paid to do the stuff that a volunteer might not want to do.
Sounds like a good idea to me.
Better and finer grained access controls is something that constantly comes up. There were even two separate full implementations of very fine grained access controls built into OH. But apparently once implemented and these academicians got their papers publised, they lost interest. They never submitted the implementations back to the project. 
There is a PR open right now with a good start at implementing this but I think it’s stalled out.
It’s not an easy problem to solve.