A thing i think BFG1 managed to do well was capture the feel of 40k. This was primarily done via the campaign obviously, but the UI and music played a big part in feeling immersed in the universe particularly from the imperial navy side of things. The way you had a home fleet type system where you could preview your ships next to amazing backgrounds also aided in immersion and that satisfaction you get from making your own customized fleet with a certain design. Especially nice was the way different factions had different looking panels when customizing your fleet. I think if this was re introduced in this game it should go without saying that it would be nice to customize the name of your ships and maybe captains as well.
Now this might be a bit harder to pull off but a thing they did in the first dawn of war game and the dlcs was to have themed music (for the main menu anyway) which added a lot to the atmosphere of the faction you were playing especially for new players like me when i was getting introduced to 40k through said games. I understand this is a lot of work but all of these things together could drastically change the feel of the game cuz during this beta the menu and what not just felt kinda cold and boring, sleek but with nothing to really differentiate it from other menu screens & UIs that you see in other sci fi games.