> You’d have to devise some sort of fire proof mini airlock

Maritime patrol aircraft like the P-8 already have such a system, for releasing sonobuoys and float-flares while at altitude.

So it's not a technical issue, more one of regulation and maintenance.

Sure, I wasn’t trying to imply that it couldn’t be done, only that it would be expensive and impractical for civilian aviation, especially when there are good alternatives.