Pretty good question. I'm not sure myself exactly other than the Secret Service protection, the interns, etc.
In all seriousness, the President of the Pro-tem committee would be responsible for coordinating the efforts of the various members of the committee such as the Secretary, Treasurer and Committee Members in charge of Membership, Events and PR/Media. I guess the committee would need to first plan the events for every quarter/year and execute them effectively.
Among others, the President would of course needs to be one who has time to spare. That is one of the requirements that is necessary not only for that post but also for others in the committee. Knowledge about Skylines shouldn't be a prerequisite as much as passion for them should be.
It would be beneficial for the Club if the President is one who is personable and carries him or herself well in public. As President, I suppose one would be the public face of the Club so its not only important that the potential Club members accept him but that the public will too. Being President means having to step in at times as Club activities will often involve the authorities and branches of the local governments such as City Hall, etc. Although this would be the domain of the Committee Member for Events, the President of the Club should always be ready and able to assist in getting approvals, etc.
Besides that, I guess the President should be one who is impartial to all the various factions that currently exist (yes, the sooner we all admit there are small factions the easier everyone comes together) and that requires a certain amount of diplomacy and discretion on his part. It would be the responsibility of the Committee Member for Membership in keeping membership dues up to date as well as maintaining the registry of members however its really the President which is the glue that gels the members together.
This is just how I view it. Some may or may not agree but my views aren't as comprehensive since I've been made aware my posts are too long sometimes. In short, the President and the Committee Members, if this Club ever does become a reality, need to selected properly as the composition of the entire Committee makes or breaks the Club.