Perhaps not exactly a cruiser, but did you know of the
Skjold class model? Also,
here is a modern-looking frigate, but it definitely needs to be retextured. And Xenomorph made teamcolored subs
here.
Those textures look horrible.

Can't really comment on the models - often I feel a model is poor, but then when it gets another texture it suddenly looks awesome.
The download page for the Skjold says there's only a shader version btw.
I've attached an excel file with what I gathered - where you could expand a bit - it's mainly keeping foils around instead of ditching them for subs, but also other tweaks. Make sure to read the notes, there are quite a lot of them to explain the "why".
Some thoughts:
Cruiser-Carrier-Leviathan are on the same tech line. For this I refer back to my comment I don't see the point in creating two ship lines which are enabled by the same tech theme. However I have an idea. Or rather I remember one of my previous intentions. More powerful submarines could be enabled by the Space and Enclosed Biosphere themed techs. I don't know if this makes any sense , but I figured the materials developed for the space industry, and the recycling technology with enclosed biosphere themed techs, would allow submarines to operate at higher pressure and deeper waters, and allow them to stay underwater longer without the need to rise to the surface or return to port for resupply. This could aid their combat usefulness.
Regarding foils, do this really make any sense in combat situations?

I figured those are useful as cheap craft for exploration, but could foils function in combat?
A cheap craft enabled by Biofuel certainly makes sense though. What's the reason for Ecological Engineering enabling a ship though? And what's behind the name Dronefoil? Does the foil launch drones (ie, unmanned autonomous air vehicles I assume), or is the foil itself an unmanned ship?
Also keep in mind that Choppers and especially Gravships should be considered part of the naval combat model.
For the graphics: The big cruiser "Leviathan"-thing from the EE2 units is pretty cool. I think you're using it for a promo-graphic of transport ships right now, but I think you could give promoted transport ships some other graphics, as the leviathan has a couple of turrets on it and looks pretty much like a big military unit (though to reinforce that cruiser-theme, I could re-skin it to make it look more metallic like the current cruiser).
I think the WW2 transport for the transport cruiser looks rather lame in Planetfall's context. I was rather thinking to use the Leviathan graphic as the standard transport cruiser graphic.
