In Tiberian Sun: Firestorm, adding "NonVehicle=yes" to a vehicle made that unit impossible to be picked up by aircraft types with Carryall=yes and also made that unit immune to hijacking. In RA2 and YR, the Carryall function works just fine, but, though there are conflicting results of various modders' attempts to research into that topic, NonVehicle= does not prevent a unit from being picked up by a carryall, nor does it prevent it from being hijacked (though a No Entry cursor appears when targeting such a unit with a Hijacker).
Could you please either restore the NonVehicle function to its Firestorm functionality, or, which would maybe be even better, include a
WeightLimit= tag for aircraft with Carryall=yes. Similar to the SizeLimit, this would prevent the Carryall from picking up vehicles above the weight specified in the tag (maybe even include this for normal transports?). To protect a unit from hijacking, you could then do another tag like "Hijackable=" along the lines of "Parasiteable" and "Bombable", which makes the unit immune to hijacking if set to "no".
Lt Albrecht:
Tat's actually quite a good Idea and would allow a lot of interesting things,for instance allowing a carryall for light units and a different one for heavy units, fixing of the ship/caryall bug where the ship can't be put back down.