Either you make it so it's an automatic self-building process, you deploy it, it builds a strip, or you make it so that individual players have to go in and create the base.
If the former, it's just a new version of the old "We want to create dirt strips in the middle of a map with dropped supplies!" request.
If it's the latter, it's taking the focus away from combat, and this game isn't supposed to be simulating what the CBs did in WW2.
Keeping the focus on combat alone, if you had a new base, where would you be allowed to put it? How many miles from an enemy base? How many miles off the corner of "no" and "where" could you place it? How many? What if some fool abuses it and places it 50 sectors inland, thus keeping folks from using it where it can be (akin to "spies" occupying CVs so their squaddies can sink 'em).
If you DO come up with rules that minimize the abuse of these "instant bases" how would they change gameplay? A massive horde of GVs (or planes, depending on which request we consider) capable of being spawned instantly anywhere near an enemy HQ or port or airfield, and what if there were 2 or 3 of them all in the same location?
I can see the appeal of including something "cool" but in this case I don't think it adds anything positive to the gameplay mechanics. It might add to the "that's cool to see!" part of the game, but how the strat/capture works now, this would be a negative thing IMO.