Hmm... ten would be a bit limited, I already get 17 action regions just by quickly going over the existing places for interaction:
- Opening/closing the outer hatch
- extending/retracting ladder
- manually opening/closing ventral payload bay doors
- remove/install port wing payload
- remove/install starboard wing payload
- extend/retract port wing pylon
- extend/retract starboard wing pylon
- remove/install centerline payload
- remove/install port door payload
- remove/install starboard door payload
- remove/install bay payload A
- remove/install bay payload B
- remove/install bay payload C
- remove/install port wingtip payload
- remove/install starboard wingtip payload
- open/close port MPS access door
- open/close starboard MPS access door
And I could easily see more places for it - like a red rapid power button on the front landing gear or more access doors for in-flight repairs. The editing of action areas would make sense for repairs, which are forcing the player to be done in the desired order.
I am sure, other add-on devs would get into similar magnitudes quickly. and the next thing I see: Once you have such a feature, add-on devs will sure find more good ideas for such actions, approaching the maximum rapidly unless you make the interface so hard and complex to use, that it hurts.
Currently, I planned to allow accessing such features over a custom function dialog in Orbiter, your action regions would be less of a work around. while the larger payloads could also be handled by a dialog inside the Black Dart, I wanted to have a lot of small stuff that can be carried by a UMMU.
Maybe 32-40 would be a better initial limit, also you should maybe ask anemazoso about his personal estimates...he wants to make Overton a UMMU compatible vessel, and could likely need more than 10 action areas over the whole area of the base.
Could you maybe allow some S.C.U.M.M (the scripting engine behind games like Monkey Island or Day of the Tentacle) like verbs to be connected to a action? Like "OPEN", "CLOSE", "REMOVE", "INSTALL", etc. A single enumeration parameter with the verb would be enough, the add-on vessel itself could decide if this works or not.
While I see the audio feedback argument, let me, in a weak attempt, add a counter argument: I don't want to torture people with my voice, when I do the voice acting myself.