Personally i think after the end mission you should get a post epilogue freeroam if you wish it, like in rdr2 can play as john marston after the ending .
Either that or wait for content drops whther new side quests, new character storys or more gigs etc
- Complete main story to unlock special repeatable challenges, which would allow player to grind for new eq, skills or cosmetic items, achievements, some kind of character challenge lvl which would boost stats? etc. (typo whatever reward you want, its just my examples). Ofc. player should be able to just free roam after finishing everything possible.
- Complete 100% of quests to unlock special quest line. Completing said quest would allow you to start Newgame+ mode. (hell, you can turn it into part of the story with some kind of time travels lol, which may unlock some new dialogues)
- Complete main story in Newgame+ mode (it should come with proper scalling) to unlock special scalling mode. Which would allow player to change current difficuty lvl (lets name it mayhem) from "NG+ Very Hard" to "NG+ Mayhem lvl 1". Lets say there would be 6 mayhem lvls. Every lvl means way harder enemies, new challenges and new unique eq. Yep... it is like Borderlands 3. But it works so damn good, and it would fit CP perfectly.
Also there should be whole big achievements table (ingame), which would reward player for ceretain playstyle.