Is there any requirement in the rules that land troops purchased in proportion to naval elements have to be on those naval elements, even if there are other troops who could be the naval landing troops?
For example, in the Early Hoplite Greek list, you can purchase Irr Ps (I) Oarsmen, up to 3/4 of the total naval elements. The list provides two types of naval elements, pentekonter Reg Gal (I) and triere Reg Gal (F). The pentekonter's troops are listed as Ps (I), while the trieres can take either Ps (I) or hoplites.
Say I purchase four triere elements, along with 3 Ps (I) oarsman elements. For the fourth triere I plan to use a hoplite element.
Come the game, I decide as invader to use impressed shipping for a flank march, using that command. Can I place the general (a hoplite) and three other hoplite elements on the four triere elements to maximise their chance of survival, and place the oarsmen among the rest of the command on the impressed shipping?
Alternatively, assuming I keep the command on table, but the land terrain is very rough, could I swap the oarsmen with some hoplites so I have some Ps (I) to go terrain bashing while the hoplites paddle around my enemy's flank?