I imagine customization for Halo Infinite at the least. If the RPG aspect is to be believed, I can imagine chief pulling off a shoulder pad and swapping it with an improved one, maybe something that optimizes his smart-link to zoom more accurately or further. Maybe there's some leg armor he can improvise that's lighter that allows him to sprint faster, or run out of stamina in a longer amount of time. Maybe there's a forearm pad that allows him to compensate for recoil more, or a helmet variation that allows him to see details in the dark ODST style.
This is what I want.
Also I'd totally love to somehow see some elemental weapon infusion. Corrosive rounds, explosive rounds, cryo-rounds etc...
Being a huge fan of Mass Effect and a shameless spammer of the Concussion Round, I support this %100. However, just not in the main Halo campaign. Although having Master Chief become something other than an unchangeable, static, faceless guy who never uses the restroom, I feel like it would receive way too much backlash, and whatever good aspects of it would be masked and ruined by the current gamer rage culture.
the idea of a knock off game that involves an RPG style would be awesome. How about ODST 2? You can customize the heck out of your trooper, his/her "class," gender, personality; the whole sha-bang, and since it would not be part of the main Halo campaign, there would be zero legit reason for anyone to whip up a storm about it.
Also, Buck would have to be in it too. They need to take him out of the main campaign and give him a large role like he had in ODST. Buck is too important, funny, and overall great to be given a small and almost meaningless role like he had in Halo 5.