There was nothing wrong with becoming emperor. The position was filled with benefits, as it allowed one to take control of resources of the entire empire, making the most fundamental problem of furthering one's magic training to the top non-existent.
No powerful mages were dirt poor.
The founding emperor of the First Dynasty had been the most powerful mage of his time. He used the spoils of war gained from the dynasty's conquest as he wished. It was a piece of cake for that emperor to craft equipment and learn anything.
However, there were simply too many who had their eye on the position of emperor. Lex had faced all sorts of obstacles just to become a viscount. She would have definitely been hampered by the House of Commons in her ascension to the throne in an attempt to share her power.
