I liked how the advent rebels have a tech that makes use of planetary population. I'd like to see all of the factions / races make use of them some how whether it's passive or an active skill. As it stands now outside of losing some tax income population is mostly an after thought. Most of the time people could care less if any of their planets have anyone on them since trade ports can make up the difference. It'd be interesting to have the populace affect build speeds, research rates or have other abilities like wail of the sacrificed.