Do your alumnae conduct interviews prior to elections? Ours do. When I was Chapter Advisor, the choices for President were, well, not good. There was a sophmore, however, who we had interviewed for a lesser office and she had her act together all over the place. We asked her to consider running for the presidency, and after thinking it over, she made the run. I'm happy to say that she went on to hold a Panhellenic office, too.
WIthout knowing your chapter personally, it's hard to make a call. Some 5-year seniors make good presidents, while others are simply burned out by then. If you're worried about gaps in responsibility, allow some of the Chairmen to appoint Assistants. That gives some of the ladies a chance to see what would be expected of them in an official position.
I would try to get alumnae feedback as much as possible. They
do hear and listen to what the chapter thinks, and who the chapter respects. See what they have to say before making any flash decisions.
Good luck!