you mean like havin a star destroyer or some big ship hovering above the ground. if the empire was in the ship, then they could have shuttles with lots of peoople and small vehicles inavade the rbels on the ground.
the rebels could have AA like you said SC271 and some good defenses and some traps
(also good places for the rebels to snipe)
I AM NOT asking for anything, i am just suggesting... 
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