I'd like to suggest the following features / mechanics for The Witcher 4:
º Character Creator / Ability to create our own Witcher (Male / Female)
º Ability to create our own Witcher School (and allowing us to recruit and even train potential Wtichers for our own School)
º Related to the above point, allowing us to create / establish our own Witcher School Headquarter(s), with the ability to upgrade parts of it (or to fortify it)
º Giving us the ability / option to go on exploring and questing with another Witcher by our side (either a Witcher we trained and is part of our School, or another "pre-fixed" Witcher available for recruitment / hiring elsewhere in the game's world as we explore it)
º Unsure if it would be lore-friendly, but perhaps allowing us to tame a creature capable of flight, in order for us to mount it to travel by air. However, I was thinking about such a creature being unique and part of a quest chain, rather than just "magically" taming one in the wild. For example, your Witcher would find an injured Wyvern youngling and, over time, you'd manage to tame it. It'd grow in size at some point ( quest completion ), which is when you'd be able to call it from any location, it'd come flying from a distance and land next to you (just as it is possible to call your horse now in Witcher 3). We'd then take off on the mount's back and travel by air up to a certain maximum altitude.
They are my suggestions for now, thanks.