I am not entirely sure how lore-friendly it may be, but would it be possible to add in some recruitable black ark mercenaries contracts? I was considering that as a base price, they cost as much as a Lizardmen Dino Rite stack for non-DE factions w/ matching upkeep cost. It would definitely require development seeing as how there have to be building limits. But nonetheless, full artillery use, limited building options, and high enough upkeep to deter unfair board advantage.
I think it may encourage some more naval engagements in-game. Seeing as how fighting pirates is a nice grind type way to level up any stragglers for the order tide war.
To add a little flavor into the mix, DE factions are able to recruit them as well but at an affinity reduced purchase/upkeep price.