While that sounds possible it is basically not .
You see even though every thing is weightless in space thrust to weight ratio still matters. And at some point the size/mass/weight of an engine gets so large that it becomes to much for it to effectively move it's self.
Now the max size changes according to what ever fictional technology that is being use but even with the most amazing ludicrous tech you can think of any thing the size or mass of a small moon would not be able to move effectively.
You be talking about year long burns to even change your orbit , and you can totally forget maneuvering in battle.