As much as love the idea of Geralt and Ciri kicking some serious ass together it just makes no sense for either of them. For Geralt, it makes no sense cos he would be letting his daughter constantly risk her life. "No Witcher has ever died in his own bed" Do you really think ANY father would let his child take up this profession if they had a choice?
But is she safer as Empress or as a Witcher,is she safe at all as empress, here is known facts:
No Witcher has ever died in his own bed - here is why : Serrit, Auckers, Letho all killed by Geralt of Rivia, Coen died fighting nilfgard, Berengar killed by Geralt or Azar Javed, Vesemir killed by Wild Hunt and then Geralt dismembered that Wild Hunt, so i think she is pretty much safe as witcher with Geralt
Now same rule goes to kings - No King has ever died in his own bed - list is much longer - Eist Tuirseach, Calanthe, Foltest, Demavend all dead because of nilfgard some of them killed by assasination ordered by Emhyr, Vezimir, Demavend and Radovid killed because of Philippa all three assasinated, Henselt, Crach an Craite, King Bran all dead, Esterad Thyssen - killed by assasins, so is she even any safer on nilfgardian throne than with Geralt, is she even safe with Phillipa and Emhyr.
She risk her life more as Empress than as Witcher