They did try in books at least and it's explained exactly why it didn't work (because women have different genetics and endocrine systems. Triss even told Geralt to stop spiking Ciri with steroids to grow her muscles, because it will hurt her...), but I see those ppl totally ignoring (or knowing jack shit of lore) as seen in
#witcherlass. Can I point out how boring all those design are and how clearly they are fans of aesthetics and not the lore? Like it's plainly stated that only Geralt had white hair...
It's canon that 8 out of 10 HEALTHY boys didn't survive. Witchers didn't even pick the unhealthy surprises to train, I think. And besides - there is magic that is capable of hardcore plastic surgeries, so my best guess, if somebody could afford it, they would just ask the court wizard how much would it cost to enable the child.
I think Ciri was somewhat considered a witcher, because she was the last person trained in the witcher arts and she calls herself that at some point. But she was very singular exception and still slightly above average human, not mutant.