Partly photoshopped mockup of something I'd been designing over the weekend. Inspired partly by the
"Raiding for Fun and Profit" blog post.
(not shown here, but deploying units also costs supplies)
The idea is that you can only deploy/move around a limited number of forces each daily turn, so you have to plan a bit on where and how much you want to commit your forces. Taking one industry at a time lowers your initial losses but gives the defenders (both surface and space) more time to respond, while hitting multiple targets at once speeds things up at the cost of higher losses. And if you concentrate all your forces in one place and the enemy hits you elsewhere...
Also it lets me partially decouple invasion difficulty from the game's ground defense strength displayed on the GUI, if I need to.
I suspended work on it when I realized it had an inconsistency with vanilla raid mechanics (both current and upcoming), and removing that would render the whole system pointless. Specifically, vanilla raids don't even pretend to have a concept of lift capacity; you can deploy All the Marines in a single drop if you want.
Fun fact: The original design before I started actually coding it was even more wackily complex. It tracked "horizontal" and space-to-surface/surface-to-space lift costs separately, and you had to drop supplies with the force on each industry and regularly resupply them (and if they ran out, bad things would start happening).
Anyway, my current simplified idea for next Starsector version is to just tweak the vanilla raid system a bit.
You disrupt all the industries you don't need to use immediately after with disruption raids, then the invade option requires you to do a disruption-like raid (that doesn't actually disrupt) on
all the non-disrupted industries (including Population & Infrastructure) simultaneously, with a minimum strength requirement for each. This means that for a large and/or well-defended planet you'll likely be spending a lot of time in orbit disrupting industries one by one till you've whittled them down enough for the actual invasion, and even afterwards the planet will be pretty trashed (i.e. not such a great prize, at least not immediately).