Though you can see it quite often building galleys the FFH AI never attacks from the sea.
The reason is obvious: It does not get it that you have to give the ship an extra cargo space to be able to use these troops properly.
IMHO this would be easily solvable by giving them 1 extra cargo space and by adding the Expanded Hull promotion to them from the beginning. That way a ship could transport as many troops as in vanilla and considering your efforts to get sailing are much higher it would be more than fair.
The reason is obvious: It does not get it that you have to give the ship an extra cargo space to be able to use these troops properly.
IMHO this would be easily solvable by giving them 1 extra cargo space and by adding the Expanded Hull promotion to them from the beginning. That way a ship could transport as many troops as in vanilla and considering your efforts to get sailing are much higher it would be more than fair.