So I off Caesar with a silenced pistol, a stealth boy, and a whole lot of running from the shotgun fist brigade. :ahhh: Blew a few heads off http://fallout.wikia.com/wiki/Multiplas_rifle along the way during exfiltration.
So I go to conclude Return To Sender, and notice that there are dialog options telling Chief that Caesar's really ill and the Legion probably won't last much longer than him. Will that result in the "Best Ending" for the Rangers?
Also, will assassinating Caesar make talking Lanius down impossible? I have yet to beat the game, but I have been spoiled (voluntarily).
EDIT: I discovered that it would indeed cause the "stop and sweep it under the rug" ending. HOWEVER...
They just linked the same dialog response that he'd give for caesar being killed, even down to the condition. So basically, you can't get the "caesar is sick" dialog unless you killed Caesar. Bug bug bug. :facepalm: