Hey Ad Astra ,
I haven't done multi-engine on a plane but I have on a tricopter , and each motor needs its own ESC . For a twin engine plane use a Y harness going to throttle channel with the + wire disabled on one ESC . And you can either Y harness into one battery or use two batteries .
On my night flyers I use a separate battery for the LED's mounted on the CG . A few of my flying buddies use this http://www.hobbyking.com/hobbyking/s...f_Switch_.html
controller from HobbyKing that plugs into the receiver ( gear or aux ) so they can turn the LED's on/off or change to different flashing patterns . The controller is powered through the receiver , but the LED's are powered ( higher voltage ) through either by a separate battery or Y harnessed into the main battery .
If you don't think the two motors you have will be enough to fly MEGA SUE , HobbyPartz has a number of motor/ESC combos with MEGA power . This one is for planes up to 44 POUNDS ! http://www.hobbypartz.com/98p-mars-b...90a-combo.html
Notice that the ESC's for the bigger motors don't have BEC's , so you'll have to get a separate BEC .