I would like to see an option to freeze XP gain.
I don't think CDPR should try to alter the leveling curve. That would maybe make me happy. But it would piss off many other players. Lots of players seem to want easy xp, easy gameplay, bigger numbers, etc. That's fine. As long as we all can be happy. Trying to tune the xp automatically is gonna be hard. And even if CDPR would fine a way to do it, people will complain. So make it optional. Just so that people like me, and others who do not want to do content while being over-level, can have fun too.
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When I am level X, and if I see a lot of quests under level X, I'd freeze my XP. I'd do those quests, and not gain XP and not level up. Until I only have quests in my logbook that are higher level than I am. Then I would enable XP gain again. This would ensure that I am always around the proper level for every quest.
I don't mind how they do it.
They could make it a toggle in the UI.
They could make it a (cheap) potion that you can buy and drink in-game.
They could even make it an option you have to manually edit in a settings file (ini file).
All of those would be good. Better than doing level 10 quests while you are levle 20.