IIRC there is a story where a statue of Tychus(I may be spacing on the name) has a statue in honor somewhere in the Ultramarine's possession, at least implying he was redeemed in the official record.
The Bulletstorm studio was recently announced to be working on two AAA titles and it'd be great if one was a Space Marine title.
Space Marines would best be represented in a Doom-like one versus a bazillion style game. Really Darktide being Guard is a bit of a loss. 4vHorde coop is perfect for Astartes. 4 flashlight boys taking down hundreds of grots is a bit of a push and I'm sure they'll be gunning down boyz and nids at that rate.
I think a Battlefront/field style game would be great for IG/Orks/Mechanicus/some variations of Chaos/Tau. Astartes would be hard to balance, other than as a general Imperium "Heroic" call in like in Battlefront. I think nids would be harder to balance unless it was a lot like Battlefront with large armies of trash NPCs and you're starting above -guants. Basically 40k Tarpit battlefield with the bigger boys being call ins.