Palatalization of C in front of i, e..

You know.. The letter G was invented by a grammarian by the name of Spurius Carvilius Ruga around 3rd century BC, and it was passed into law by Censor Appius Claudius Caecus in 312 BC.
The letter G was created because letter C had 2 sounds.. One hard (K) and one soft (G).. and Spurius Carvilius Ruga wanted to put that difference to paper. To demonstrate it. So he added an extra line to the "C" thus creating "G."

The very same process would have occurred when V branched out into U and V, and when I branched out into I and J..

I am not sure I agree with you that the palatalization of C occured as early as you predict.. I think the general consensus is that it occured some time between 300-450 AD. But I haven't studied this intermediary face much, I've mostly studied on the great change from the hard "K" of "Caesar" (Kaisar) versus the palatalized C in "Cesare" (Chessare) in Italy today.. and of course the G in "Giovanni"..