Why isn't anyone asking for marines? Marines are great, historical and woul open a lot of strategic possibilities. They could be similar to commandos, but with some diferences:
SPECIAL ABILIITY: Disembarking time reduced by 50%
BUILDINGS NEEDED: Barracks lvl 2, Industrial Complex level 1, Naval Base lvl 2 (no need to be at your capital)
COST PRODUCTION: Same as commando's
UPKEEP: 90 Food, 110 Manpower (same as infantry)
UNIT STRENGHT: Same as commando's
TERRAIN PROPERTIES (HP, Unit Class, Strength Modifiers):
Same as commando's except by those two:
Mountain: -50%
Urban: -25%
UNIT SPEED: Same as commando's