Not sure what do you mean by "Cyberpunk's higher focus on optional and more fuller side quests"Tbh I'd like to have "Witcher 4" similar tone that Cyberpunk had, with ability to create own character, with different abilities are specializing into multiple roles. Strong main story with plenty of narrated side quests (hopefully not too many quests just to go X and kill Y", at least without dialogues on why to do those fights).
I think sticking with Witcher 3 open world might not be good in any other peoples eyes aside from the "I completed Witcher 3" completionists, like 50% of playerbase has likely even finished main quest and of those maybe 10% has finished more than 10 side quests. It's still a large audience for sure, that might be the most passionate people to boost and recommend the game to popularity, but I think Cyberpunk's higher focus on optional and more fuller side quests seems like far greater approach, even going further and almost cutting away those smaller side quests entirely.
So not sure you even played the game, but The Witcher 3 offer way more side quests than Cyberpunk (and it doesn't take an account "unknow locations" and "contracts" which are equivalent of "NCDP Scanner hustles" and "GIGs" on Cyberpunk), so check here to have an idea:
The Witcher 3 secondary quests
About main/side quests, both games are very similar