We have a tech priest and a tech marine I'm sure the machine spirit of smaller vessels like something we could manage now eg: bomber, armed Cargo ship. Rather than a ship we might be able to get working eventually. 

A corrupt eldar ship crewed by demons is a beautiful idea, when we might have time to sort it out. But trying to manufacture chaos servitors on the fly dying a battle... I call BS there is no way we would have time to board, capture and build spawn. Not to mention the lengthy research process of trying to make servitor spawn. All this before the battle is long over and we are torpedoed to death or boarded by a few squads of Terminators or whatever not a chance.

Smaller steps man. It's not that it can't be done, we just do not have the means right now. Steal an imperial bomber, find a secluded place, figure out how to make servitor spawn or start kidnapping regular people and making regular servitors and start moving up the ship class ladder.