can you make a mobile attack without moving in order to combine fire with another unit? Could you simply move out of your hex and then back into it to satisfy the mobile attack requirement?
You make a mobile attack by moving up to half your movement allowance and firing at half firepower. Not moving at all fits the definition of "moving up to half your movement allowance." So yes, you can combine fire with another unit making a mobile attack (at half firepower) without moving. No need to move out of and back into your hex.