Or, by way of option 4, do the PGCE in business. Once you are a qualified teacher, you are technically qualified/can be asked to teach any subject relevant to your skills, so presumably you could always express a preference within your school to also teach history should the opportunity ever arise. Do keep up your interest in history though - attend conferences, read books and so on - so as to keep your toe in the water and show to schools that your subject knowledge is current and your interest active.