Luckily by being an open choice. You can do all jobs on one character, or start a new one and do a separate job. Keep in mind you have to repeat low level quests and unlocks, as well as have 2 roles to do the other job. so it will be very time consuming to do that, and other content.

If a person has that kind of time on their hand they can do that, but many of us work ful ltime jobs, have school or continuing education, and it isn't viable.