I am not sure whether your mission is primarily aimed at SP or MP and that's a little relevant.
In MP available player gameing time and maintaining the connection are limiting factors.
There are two schools of thought the previous NCHQ type players who feel that realism is foremost.
Starting positions well spaced to allow for the sort of RL care required in careful scouting, feeling for a
position, stealth, closing the odds down etc. On the other hand , we have players who rightly demand action/fun
within a shorter timeframe, determined by the factors above.
Harpoon faces difficult ballance issues . Many find the action too slow and in SP the remedies
are to hand. But with the new MP Harpoon Beta when do you agree to accelerate ? Can you ?
For SP what ballance ? One would not satisfy the gamer who posted that he had given up an anticedent
of Silent Hunter from boredom. ...........When challenged it transpired that he never used any in-game acceleration.
That must also be compared with the guy who played SH in realtime, over weeks, posting his action (sic) almost daily.
For me the limits would be a MP mission lasting no more than 3 hours and a SP one 2/3 days,
with average(?) gameing time.
But surely if the MP mission is designed not to 'overload' the connections, as long as the proper health
warning description is given by the designer, those who choose to play a more realistic mission will queue.
Especialy when they see the plaque on the door !
PS. ** I see no reason why a ( none platform sharing ?) MP mission,, could not have goals set at different intervals. The players could decide whether to participate in a 2, 3 or 4 course meal.