May the time of refilling the energy be at least decreased? I noticed the further the campaign goes, the more energy is needed. (I mean, it should be that way, right?). Right now, I need 5 fuel for 1 Hard Mission. So... We have maximum of 20. That means I can only do 4 missions. How much is the time needed to refill 1 FUEL again? Yeah, that's right. 7 minutes. (It takes approximately 140 minutes to fully refill. That's nearly 2 hours and a half!) Waiting that amount of time vs. the amount of missions you can actually do is pretty ridiculous.
I honestly think it should be only 3 minutes per 1 fuel. 7 is just too much. Come to think of it, this kinda reminds me of the fuel mechanic of the FB game "Tetris Battle". Though I think it's only 5 minutes per 1 energy. Still though, 3 is the most suitable number for this case.
Additional Suggestion Involving Campaign Fuel:
Remove the fuel once finished in insane mode. People who likes to grind in the lair of "BIGBOY" (like me) would hate the fuel mechanic right now.