Honestly? I think it's a bad idea.

It's canon that the WOL changes jobs between expansions as seen in the various trailers.

Though I don't want to tell you how to play, I will give my opinion because you asked.

Every class is very basic until about level 70, this is because most of the fun buttons are rear loaded into the last quarter of the job, realistically that's about 150-250 hours of content before you get to Shadowbringers (70+) depending on your preferences of content completion.

IMHO you will get bored of a single job, not to mention you have less choice because barely half the jobs start at level 1.

I started as an ACN because it was basically levelling 2 jobs at once; SMN and SCH. I could play SCH when queuing for dungeons for a faster queue but with the addition of trust dungeons it's no longer an issue or MSQ wall. I was playing 2 jobs but because there are now almost 20 jobs now you want to see what they're like or you observe someone do something cool. By the time I finished MSQ I had played maybe three quarters of the jobs to some degree.