"One end of the PCB could be the power end, both sides - whilst the other end would be control, both sides. "That's what I was saying in #9.
I would use as much free area top & bottom for ground polygon as you can.
I can see a potential problem with using global fill, in that it violates the star-groundingidea.
Is this diagram the same thing we've been talking about for the past few days?
I don't see anything about separate power input for the h-bridge, or main caps
But you have to do what you have to do, and see how it goes.
The further away from the connector that the h-bridge is, the more possible noise it'straces can propagate to the rest of the pcb cktry.