I have never played Orks, but i like the ram-ships. I would try to avoid the dependency on command checks if possible - they should have ordnance, but ordnance shouldn't be their main weapon. Try to rely mostly on weapon batteries and ramming.
Edit: Kill Kroozer, Onslaught, Brute, Dethdeala, Hammer, Grunt. These i would use as core, with some of the other optios for variation/experimentation.