Hire a sub developer to remake a bunch of the halo 2/3 maps in Infinite and add a classic mode in Infinites multiplayer. I know we have MCC but those old Halo games are really starting to show their age at this point. Besides, the multiplayer doesn’t really feel the same as the OG 360 games anyway.
Seeing as the core gameplay feels very halo 3-esque to begin with, this seems like an obvious addition for some content that would be well received. Heck, it might even turn out that some of those old maps would be good for regular social playlists anyway.