jolly, we used to have a mission building system like that. You could make several different 'flights', even of the same type of aircraft, that could up at different times and at different bases, while all in the same mission. It was pretty nice to have once in a rare while, but making simple missions in general was much more difficult and time consuming because of the complex setup.
Factoring in that fact and the fact that complex missions had become extremely rare, HiTech toned down the mission interface quite a bit to make it simpler, more efficient, and faster.
Personally, I wish you could choose between either type when creating a mission... but to be honest it really wasn't worth all the extra hassle for the few rare cases that you would actually use those features...
