Mille viae ducunt homines per saecula Romam - "A thousand roads forever lead men to Rome." Caesar tells you that what he wants and what he needs is a Rome - a city and symbol around which to base his Empire. A central place for his idea of culture and society to take root and grow outward to the farthest corners of the empire. When you meet him, he compares himself to a barbarian king stalking around the gates of Rome. One has to remember that Caesar claims that he is a son of Mars, like Romulus. And Romulus founded Rome, so Caesar, too, intends to found his own Rome. Of course, Caesar has won other cities, from Flagstaff, AZ to Denver, CO, but none of them have given him what he really wants to make as his centerpiece for the Empire. Whatever he is looking for, he believes he's found it in New Vegas. That's really what's most important for Caesar's Legion to continue on after Edward Sallow - a symbol and structure for which the people will continue to follow. When the man is gone, the city he leaves behind carries on. That's what Rome was in ancient history, and that's what Caesar is trying to accomplish by capturing New Vegas. Once he takes New Vegas, the implication is that Caesar will turn New Vegas into a New Rome. He will then transfer the cult of personality based around himself and then transplant it onto the city. Instead of everyone following Caesar himself, he intends to make everyone want to be a "Roman" (or, perhaps a "Vegan?") by building up New Vegas as the center of the world for the Empire.