Having done both, I don't think pre-requisite airman service is really a good idea. I got enough hassle for being a mech-tech let alone being a future guaranteed officer. I learned a lot from the ranks and it has certainly helped me in the commissioned world. There are a few major companies that insist their graduate programs spend time on the shop floor; Aldi's management training scheme for one (I'm sure someone will correct me). Believe it or not, the Air Force actually needs Ox-Bridge graduates for higher up the food chain. It may take some time for them to learn the job, but isn't that one of the roles of the FS and WO - mentoring Junior Officers?