In a case where the pilot never dismounts, and a TAG is either unconscious at the end of the game or killed outright, does this qualify as a killed specialist in ITS missions?
nope, the pilot profile was never used at all during the whole game, he can't count as being a dead specialist. edit: also, the TAG by itself cannot count as you having a specialist in base contact with whatever objective that give point at the end of game for having a specialist in base contact with it.
No. See the FAQ: N3 Frequently Asked Question FAQ Version: 1.3, Oct 2017 Q: In the scenarios that grant objective points for killing Specialist Troops, would the elimination of a TAG be counted? A: No. It would be counted only if the Pilot or Remote Pilot was killed, while dismounted.