Actually the tall, vertical structure gave me an idea just now. You would want to tuck in the engines on the sides/puff out the troop compartment, but I was thinking that with tall ships like this you could have them slotted next to each other on the underside of a Capitol ship. That way with the tall and thin arrangement, you could get more transports off faster, no waiting in line to get out the hanger and you could fit more vertical gunships than with a horizontal configuration.
Plus when they get down, Vertical structure gunships could make a better wall, if they're going to stick around.
As for the grey vs. white, well that depends on your faction colors. If you don't have one, then I would default to whatever color you have most of. As it is it looks like some kind of prototype related to the LAAT Republic Gunship.