Something that I've not found myself able to do, and would be hopeful of, would be a way of transporting population between systems without needing to colanise new planets. Colony ship transportation of population doesn't allow reinforcing an existing population which would probably be the easiest way to do this.

This would allow for tactical distribution of your population and also a way to relieve some of the over crowding in some systems whilst augmenting systems of tactical importance more quickly.

+1 I've wanted to accomplish this on a few occasions and was disappointed. Ie why not a under civilian mods add 'civilian transport' module.