I really want to agree, it feels right for orks to have higher hits on their battleships, by slapping on a bunch of gubbins and positively packing it with ork crew. But some thoughts keep me from agreeing.
1. Every ship I can think of beyond 12 hits, besides monstrously grown hive ships, were made in the warp or constructed by the Old Ones, likely in the warp as well.
Planet Killer, Hulks, and Blackstones.
2. Hulks are a different story than regular ships. One could say that beyond battleship hitpoints, anything Orks create would function as a Hulk.
Orks essentially find them premade, and reactivate/tack on new systems to give it some semblance of mobility, but its nothing like a true warship.
3. It is stated in the fluff that Orks salvage battleships, but rarely use the chassis because the level of technology is beyond them.
Essentially, 10 hit kroozers are that big because its as big as orks usually go, because we all know orks greatly desire to be as big as possible.
There are a few notable examples of larger 12 hit ships, but as difficult as it is for the far more advanced IN to hold similarly ships together, gestalt conciousness only goes so far I'd think.
So in conclusion, maybe a 'lite hulk' or a very slow and unwieldy warship could exist in the galaxy as a 14-16hp character ship, but I don't feel its a hole thats missing in the ork fleet.