Is there anyway to add custom made systems to the pool used randomly by Galactic War? If so it would make the mode a lot more interesting.
Pretty much everything in GW is determined by the client. It should be possible, but it might be a bit tricky to figure out how things work and modify it. For one, GW wasn't built to handle all the extra data for the fully custom planets. It also looks like it's using a file shared with the main game, so you may want to make copy and redirect the GW references. Starting point: media/ui/main/shared/js/star_system_templates.js