Patches take about a week or two to completely clear for most people unless it's a new expansion. You have well over a year an close to 2 years of down/free time to level extra jobs, heck a lot of people max all jobs each expansion for the bonus reward you get starting from ShB. You can't not have the time to level up a new job for a story or bonus content between, unless your choosing not to.

Pick a class of each type with summoner or scholar being one as you'll freely level the other at the same time. Then just focus on those 4 classes till each are capped, solution solved. If you don't wanna do that buy a class skip.

There has to be content locked behind stuff other wise the game would be barren with people playing for a week and then leaving for the next 4 months between patches.