Will it be viable to spread out your forces? The original (Likely due to it being so unpolished, not by design) seemed to make it so multiple companies were almost always needed to combat a threat without taking unacceptable losses. Is that viable or will you need to be more dedicated in your engagements?
My
goal (which is very much not represented in current gameplay) is for there to be way more things going on in the sector than you can possibly deal with at once. If you undercommit forces, you increase the chance that not all your brothers come back. But if you overcommit your forces, then there are that many more problems in the sector you're not dealing with. This will likely include a mission system in addition to the pitched battle sim that's currently in the game. The idea will be that there will be relic hunts, recon, assassinations, space hulk explorations, and other sorts of special ops missions you'll be able to send forces on. And maybe, sometimes, the group you send disappears without a trace... how much larger a force do you send to find out what happened to them?
My other long-term goal is to have more examples of your forces augmenting Imperial engagements, rather than fighting as the sole unit on the field. I'm not sure yet whether I'd represent that via the mission system or the pitched battle simulator.
What's going to be interesting to balance as I go is the mortality of a Space Marine. I don't think tabletop (in which a large volume of gretchin can take out SM with peashooters) nor fiction (where every Space Marine has invulnerable plot armor until the story requires that they die in droves) provide the balance I want. In the system as implemented right now, it's far more likely for a Marine to drop due to having a leg blown off than to actually die, but that could lead to everyone in your chapter having massive bionics after a century, which doesn't quite match the setting (well, except for the Iron Hands, of course).