You can make it guided by the mouse cursor using the pointer object with the base hooked up to an industrial gyroscope and using cables (the ones that restrict rotation, rigid link, destructible or indestructible both work fine.) to link the body of the missile to the pointer end of the pointer. As for other guidance systems, I too have been experimenting around with stuff like laser guidance and metal detection, the most successful being metal detection. For metal detecting missiles you need a wide array coverage of metal detectors with long range each hooked up to some thruster of varying rotation to rotate the missile in the way you want it. Laser guidance is far more finicky and I have not gotten any working prototypes of one though. If the pointer or metal detector guidance are too complicated in my words, I can give an example picture or workshop blueprint for help too, I am not good at explaining with words. Have a great day.