Being that this is a public forum, I hope you don't mind my tuppence's worth.
In my opinion there are two key criteria for a good Baron.
1.) Regular play. Doesn't mean you have to be in the land 24-7, you should be able to do an effective job with a couple of hours or so a day. But checking in often is important, I feel.
2) The ability to do the job. In other words, a sense of fair play, an understanding of the city, the ability to listen, thoughtful, fair and calm leadership.
Age, fighting ability and so on, in my opinion, don't really come into it. If you work hard for your city, in whatever role and are respected by the citizens (and please don't confuse like for respect), then there is no reason why you should not take on the role, should you gain the votes.
Presumably anyone standing for Baron is doing so because they actively wish to be involved in working for and improving a city, and importantly, one who shares the vision of, and wishes to work with the Prince/ess. Unfortunately, that may not always be the case, but really and truly, it is for the voters themselves to discern which candidates are valid and it is not the place of the Divine (Patron apart, perhaps), or indeed, non-citizens to do so.
I only post as this might be an interesting topic for discussion, given all the recent stir around various elections - I don't pretend to think that I am the only one to have an opinion on this matter. I would definitely be interested in hearing whether people agree, disagree or have other ideas. I for one, am not even sure that I am a fan of the current election process, given the fact that it lends the opportunity for so much instability and with the option for Barons to be voted out before they have
even been given a chance to prove that they are any good in the role. Can't really see how it could be changed for the better though...
Written by my hand on the 24th of Cloudburst, in the year 1328.