It would not unbalance the game strategically because it is an easy to shoot down plane.
I have read it could take tremendous amount of punishment. Yes easy to hit, but hard to bring down. They actully used fighter-bombers and planes like b-26 to shoot these things down over mediterranean.
The Gigant could carry a Marder, which was a decent tank destroyer based on the PzIV chassis.
Actually, Marders were built on Pz 38(t), Pz II and Pz I chassis. Gun was 75L48 PaK or 76L51(r) captured russian gun adapted for 75mm ammo. Marders had good hitting power but not much armor to talk about. Their main role was in ambushes and defense. Very much like towed PaKs were deployed.
The Gigant could not transport any of the vehicles we have in AH.
All other Ostwind and PzKpfw IVh not included.
Something that it could transport: FlaK 88mm/sIG 150mm(and all below)+SdKfz 7 Gun tractor(as seen on pic above), light pazers, armored cars, Flak vehicles(not flakpanzers), Marders and some better armored light panzerjägers like Hetzer (nasty little bugger good gun and well sloped armor)...and many many men.