Regarding region lord actions:
The system used to handle this is actually pretty antiquated, too. It would be better to replace it with a system that actually tracks individual actions done, and knows which ones should block others.
That said, the actions you mention don't sound like they should actually produce those results.
First, were you building fortifications, or repairing them? Because from a quick scan of the relevant code, it's only repairing fortifications that should block holding court (which is, itself, pretty messed up, because you'd think there would be more people involved in building new ones...).
Second, when you get a chance, can you please try holding court, then building (or repairing, whichever one you did) fortifications? Because they should mutually block.
Regarding unit-related actions:
This one's a separate, but relatedly irritating, kettle of fish.
I believe (off the top of my head) that the issue with hunting is less that it blocks other actions, and more that performing other actions after sending your men to hunt cancels the "hunting" status. Ideally, this simply shouldn't be the case: hunting should be something that you men automatically do after all the other stuff you have them do during the turn; otherwise, why would it just cost the 3 hours and then let you spend the hours on other stuff? It certainly shouldn't be cancellable without warning.