I ban DN 'cos, Orkified Space Hulks are actually a frequent occurrence. Small (relatively) Ork warbands use those as a transport ship capable of carrying the entire warband and their belongings (perhaps even starships) through the Warp from point A to point B. Or C. Or D, or... doesn't actually matter where, all that matters is that there should be a lot of enemies to fight, the more the merrier. Ideally there will be enemies on the Hulk itself too; genestealers, nids, Chaos daemons, 'umies looting stuff (AdMech and Dark Mechanicus pay a premium for tech one cam find aboard ancient ships fused into hulks), other Orks, doesn't matter either.
Orks actually using it as a battleship, however, happens rare. But then again, Orks as a faction don't have an aim to defeat all other factions; all they want is to keep the WAAAGH going forever.