Thats the point. There was no real Roman nobility. The plan was more or less to gather the richest and therefore most powerful families living in rome together with some langobards and have them proclaim him emperor. Benefits: The people who gave you the title dont have actual pover to take it away from you and you and you sucessor never will have to worry about it anymore. The pope on the ther hand showed what a little shit he and more importantly his successors could be
It took quite a while for the popes to be capable of really influencing things the 11th century and beyond.
Riain: Your (and my) favorite Komnenoi emperor comes to mind.
I dunno about the first in honour/first in rules, but I could see that - it seems very appropriate for how the Byzantines treated the issue.