I think there should be 2 types of cargo choppers. One able to carry only foot units (infantry / settler / worker / explorer / spy / Great People / etc...) and another one able to carry every unit that moves on land (armor / mech infantry / artillery included).
Each shopper should be able to carry only 1 unit.
When embarked on a ship both the shopper and the unit should count for the cargo limit.
Now, my question is should the chopper be transported by sea on transports, aircraft carriers or a new unit, the "assault carrier", or something like that, that can only carry choppers (with or without cargo) and VTOL aircraft (yup, another new unit)?