What I would want, Which was the main idea of my *Fleet Command* suggestion, before I kinda got carried away, Was to have control groups that would automatically re-build ships, when the control groups were on a planet with a factory in that control group.
That way, Control group your whole fleet when you build it, as well as a factory on your main planet (ofc you could share them between groups, but that would require some careful coding)
The other significant points, were that your control groups would also reserve ship caps, so that any other, say, autobuilding factory, would not steal half of it's fighters after they got decimated, but rather reserve them. That way, you could easily replenish your fleet, without much issues, so long as you build the whole fleet, and then control group it.
The reason this pertains to this suggestion, is that the main way people select their fleet, is to drag a box around it, rather than using control groups, because rebinding ships to control groups is takes time, even with the ability to bind factories with that (which adds built ships to the control group automaticalls) since that would still require you to build the right number of ships.
