Extremely easy w/ Darkness Energy Recharger and Ultra Bomb from legendary shop... sit there nuking and dodging constantly and then just recharging your energy in like 10 seconds... bosses can barely shoot through all the nuke push.
I won on 10 by just making a push for water control... I managed to get 2 cruisers out there and then just held then off w/ stealth tanks while my cruisers pounded their static defenses... needed planes too to defend cruisers from hindenbergs
After experiencing the game in it's entirety, it's a pretty neat game. Good story/concept. Only problem is the story/concept is not clear at all if you're not paying close attention or just futzing around with the game to start.