If you put in characters you can come across in Cyberpunk 2077 named Ciri, or Geralt, or who ever from Witcher, that looks and sounds like those characters, that could be thought of as being those actual characters that somehow magically have managed to get into the world of Cyberpunk 2077... then your doing it wrong. There is no magic in Cyberpunk 2020, and there should be no magic what so ever in Cyberpunk 2077 either. Doing it this way would just not fit into CP2077, and you would me mixing and matching IP's and diluting what something like Cyberpunk 2020 was and is.
What I personally would not have a problem with as a Witcher/CDPR easter egg inside of Cyberpunk 2077, would be if anything Witcher related was refered to as an actual product that exists in the world, and/or a company in the world names CD Projekt Red... because Cyberpunk 2020 and 2077 does take place on earth with an altered history (not sure at what point history diverges in CP2020/2077 from our own)... so as such it is not inconceivable that in the past in the CP2077 universe there was (and maybe still exists) a game development company named CD Projekt Red, who made a fantasy game series called "The Witcher".
There are a few scenarios I can think of that would work well with having these kinds of witcher easter eggs.
The best case scenario for me would be somehting like that you can find some kind of retro gaming bar (where you have to do a part of a mission or something), where you can find all kinds of oldschool gaming stuff, be it old arcade machines, old computers with old games installed on them, posters on the walls, maybe display cases of old action figures of characters from these old games, etc. This is maybe where you could play something like the Witcher card game or something (if there is going to be any kind of mini game in the game that is).
The reason I feel this would probably be the best case scenario would be because there is always going to be people that are obsessed with old stuff and/or with certain cultural aspects from history... and seeing as how big gaming culture is today, chances are there is going to be a fair amount of that which manages survive into the year 2077 and be vintage and retro and "cool again" or what ever, stuff which people would want to collect or be around or what ever... so such a bar would be perfectly reasonable to exist in the year 2077.
Heck, maybe there is some kind of gang which runs this bar who base their look and what not around old retro gaming stuff... since most gangs I have heard about from CP2020 (being on this forum for a few years now) do seem to all be very unique from each other in anything from looks, and what they are about and what not, what their "thing" is, etc.
Another version could be that in one of the missions you have to break into some kind of gaming studio for what ever reason, which happends to be named Cd Projekt Red (or something very simmilar), where you could find simmilar thing as to in the above retro gaming bar, but mostly connected to CDPR stuff. I prefer the above retro gaming bar though.
But yeah... if there are CDPR/Witcher easter eggs in CP2077, then this is what I would prefer... that the Witcher stuff would be refered to as actual producs in the world, and CDPR as an actual future version of the company. I don't want anything Witcher related thing to be refered to as actual people/world that exists in another dimention in the CP2077 world... because as I said, magic does not exist in this particular version of the Cyberpunk genre, it does not exist in CP2020.
There would be no use of magic in the gameplay, because it would draw the attention of the Wild Hunt. Although this is of course not a serious suggestion, and is unlikely to ever happen, it is still a somewhat interesting idea to play as a pre-defined character, but in a futuristic world she is not familiar with.
