I think I can help you a bit because small RC conversion is where my interest lies. Check out this very small motorized ship https://www.youtube.com/watch?v=qFt5j1HjsVw
The problem with this Revell model is its narrow width, NOT like battleship's wide body. This creates the high centre of gravity problem, causing it to topple over. If you insist on doing it, it could be done with some sacrifice of authenticity. If you are a die-hard modelling purist, I say don't bother, it is impossible. 1) Lower the high c.g. by reducing the height of the masts if needed to. Use high tech low weight carbon fibre rods. Thin the plastic of upper decks & funnel. 2) Buy Macro- helicopter small motors & mini Lithium batteries to use. 3) Use RC system from small toys, which will be servo-less & light. 4)Test with different ballast weights, most likely you have to put it outside the ship like those RC sailboats.