I feel that with ArmA III - while the MBT are totally fine with their huge beefy armor - that APC's (that should make most of a fighting force on an island as Stratis/Altis) are really TOO vulnerable to any threat : may them be on the ground or in the air.
RPG and PCML(NLAW) will wreck any kind of APC in 2 hits and while RPGs are kinda "dodgeable" it's way harder to avoid PCMLs. Let's not even talk about Titans who are going to transform an APC into blazes with one single shot without any chance for the vehicle to survive.
So I don't know if it would be realistic or not but for gameplay sake I humbly ask for a "life-insurance" for the poor crews in those vehicles as it can be really frustrating (especially in PvP)