Upon reading the name of this thread I got this weird mental image of Marcus the supermutant stabbing Caesar to death.
Anyways, it would have been interesting to have a quest that offered a more historic death for Caesar, but imo it would have been kind of a cliche. I mean, the Legion replicates ancient Rome militarily and in some ways socially/politically, but it really wouldn't make sense for the death of Caesar to replicate the death Julius Caesar.
I asked JE Sawyer on Formspring whether or not a Brutus type character was ever planned, so maybe we'll see an answer there, but my take on it is that the devs wanted to write their own story for the Legion rather than copying history too much.
Edit: And there is the quest "Et Tumor Brute," so there was a reference to Brutus, or rather Shakespeare's take on Brutus and the whole assassination.