iki
Warlord
Concerning polyps and the blue rocky resource, I'd say the polyps will be a food source and the blue rocks will be like gems from civ 5 but situated on the sea--that is, production and energy.
Speaking of strategic resource uses for hybrid units, I also agree it should be more expensive.
But it should be more or less on par with the equivalent parental affinity versions.
Supremacy / Harmony might have the bonuses of working in tandem with other units, but maybe the move speed of Harmony.