Also, I don't think the Federation would require its Presidents to only be natural-born citizens. Too many worlds are likely joining the Federation all the time for that to be practical; you'd have a situation where an entire planet full of potential Federation Presidents would be discriminated against for the highest office for upwards of thirty years after a planet joins the UFP. It seems more rational to me to hypothesize that the Federation Presidency is legally open to any Federation citizen, irrelevant of whether they are natural-born or naturalized citizens.
I am pretty sure if the Federation had a natural born citizen requirement, which I am not saying there is, they would apply the natural born citizenship retroactively to all natural born citizens of a newly joined planet. That would keep any, if any, benefits of the natural born citizen requirement and not needlessly discriminate potential Federation Presidents.