Ok, so now that I've discovered it would be a huge amount of effort to add in new blueprints for every faction myself, I thought I'd try to sell Stardock and my fellow gamers on the idea that some new blueprints might be good additions to Crusade. Here's what I was thinking of, just a few ideas based on my gameplay experience:
1) Cargo-hull combat variants: because of the way combat works, you don't have to waste military hulls on combat support ships and carriers. Auxilliary Carriers and Auxilliary Support Ships are useful in battle, and cheaper than their hit-point-having counterparts.
2) SWACs, aka 'sensor barges,' aka 'electronic scouts' aka 'scouts'*: these ships are mostly or all sensors. I usually have one based on a Cargo hull (my standard SWAC), and one based on a Huge hull (the fabled 'Eye of Sauron'). They are very important, especially on large maps where situational awareness is especially vital.
3) Fleet Scouts and Auxilliary Fleet Scouts: why does every ship have to have sensors on it? A Medium- or Cargo Hull can carry more sensors, and can stack with the fleet, increasing its sensor range and saving valuable volume for weapons on the rest of the ships in the fleet.
4) Sloops (aka cutters, aka fast frigates): especially on large maps, speed is important. I typically have a small cadre of sloops, which are about twice as fast as normal ships. These do 'cavalry' jobs, like intercepting intruders and running around behind enemy lines blowing up asteroid bases. Because Tiny hulls are generally useless, these are usually Small- or Medium hulled.
Also, in general, all warship blueprints need more engines (I'd argue, fewer sensors and life support, too). There is no use for a speed 6 ship on an Insane map! It is basically a weak starbase.
* A SWAC is a scout; a 'physical scout' just moves faster farther and has less sensor range, but they both do the same job: locating objects in space.