It's not hard coded.
You can open paratrooper.txt in DH Full and remove the "#" before any brigade you want. By default, all brigades for paratrooper are disabled by those #.
I just allowed them to have Artillery, added paratrooper tech to GER 1936 to test, and it worked.
It'd be good if there was a tech line for airborne brigades, like extra equipment, small artillery and eventually things like jeeps... you could have gliders somehow.
It's not too hard to make a glider or jeeps brigade, I think
My solution is to change
- R.Art (which is now Cav brigade) -> AA (so AA and SP AA is near each other, since SP R.Art was made SP AA)
- change AT (which is now M Tank Brigade) -> back to to AT (TD is seperate from SP Art, so no reason why AT the same as Art)
- group M Tank and L Tank brigades together in a new brigade category called "Tank brigade" (but allow the latest L Tank brigade to stay active and does not upgrade to M Tank, by using that new "-2" stuff)
- group SH Tank and H Tank brigades together as Heavy Armour (Super heavy is useless anyway, but make H stay active and not upgradable to SH)
- change SH Arm -> CAV (it's neat to have CAV before AC, as they have same function)
- That leave AA (freed) -> glider (paratrooper only brigade), add a bit of hard and soft attacks, plus org since it help concentrate landing and provide heavy equipments
So the brigade line in production menu is something like this
ART, SP ART, AA, SP AA, AT, TD, ARM, H ARM, CAV, AC, GLD, MP, ENG
Haven't tried it though = p
as I'm waiting for a newer version before starting to modifiy the game heavily to my thoughts