This question has already been asked more than once, there were suggestions that we could send transports to the second mission at once. But the proposal was rejected. As far as I remember, for technical reasons. All soldiers after the mission are considered already in the base, all the wounded are being treated, all stocks on board the transport (weapons, ammunition, and so on) are replenished. That is, on the second mission, the transport would fly in as if it had flown into the base before, leaving the wounded there and gathering new supplies, which looks strange. Well, at the same time this restriction is taken from the original game and they decided not to cancel it.
P.S. Simple mods do not achieve this effect. You need to change the OpenXcom.
