Wait, are you saying that since the Vitas of CC were named for the Fates that there couldn't be a connection to Atropos from CT, who was the first character in the series to be named after one of the Fates?? How is that not a striking connection? It's even relatively easy to connect the Vitas with two other characters (or components of those characters anyways) from that first character's background. I agree there's no definite answer, but it seems like a fairly big coincidence for there to be no relation at all...
If nothing else, it's probably a quirk of the Mother Brain that named Atropos that way, since Atropos in mythology was the eldest sister who cut the threads of fate (much like Mother Brain was trying to accomplish with the humans)...then the Mother Brain was ironically used to create FATE...perhaps it was those remnants that used the knowledge of the Fates to create FATE's 3 guardians...or else it was the creator of FATE that remade Atropos, but chose to include her 2 sisters as safeguards...FATE itself really imitates the Fates of mythology when you think about it....
XR is her model type. Robo is an R-type. XR probably means she was the first of the R-types..."X" is usually connotative with experimental in these terms (ala PSX).