Reasoning behind this "wait for N turns to use explosives":
1. Aliens are turned towards the craft since first moments of battlescape (all 100% of them for superhuman)
2. 2/3 vanilla crafts (i.e. most of them) of XCOM1 have wide opened access during AI turn, and they simply can blast whole team. Lightning craft doesn't suffer from this issue, and technically if you're using it, you won't suffer much from AI being using grenades from the beginning.
TFTD crafts don't have widely opened doors (all crafts have auto doors), and this "wait for N turns" becomes obsolete at least, and really gameplay altering at most.
The weapon list, which can cause this "storm of whine" because of vanished team in 1st turn, is much shorter than list of "issue safe" weapon. Logicaly, it'd be much easier and better to make this variable exactly for the alien grenade and blaster launcher. There's no other weapon causing initial issue, and no need to touch anything else. And by default all kind of weapon is usable from the beginning.
And since TFTD is in development, this change is in "todo". And really, there's no need to bump this thread endlessly.