Speaking of Star Trek, Worf from TNG eventually became a regular on Deep Space Nine but he didn't take any room away from the new characters. I see Lelouch's involvement as something similar to a famous guest appearance or even less intrusive, since he's got another persona and the core narrative isn't constructed based on him. Lots of stuff happened before he arrived. I see him as a factor that will bring chaos to the situation, but the actual web of character relationships goes around Julius, not through him. Akito and Shin aren't at odds because of anything Julius did. Leila is curious about Akito and has to deal with the new Japanese characters as well as her superiors, etc.
To make this semi-relevant, the homepage for Akito has a new main image.
http://www.geass.jp/akito/
Lelouch/Julius and Suzaku are there, but they're a bit smaller in size than Shin.
They're not on the Limited Edition packaging for the second episode though, which has Shin and Asura.
http://www.geass.jp/akito/bddvd2.html