So there is a JP+ skill after all. I didn't bother long with Freelancer, only up to level 4 and even then only to complete the tutorial quest; otherwise I would have moved on earlier, because I already had four non-Freelancer jobs at that point. But that means I could have had 20% extra JP all this time.
I see someone never played Final Fantasy Tactics. It's tradition now!
Only played the FFTA games, I doubt that FFT is much better. But anyway, am I supposed to look up FAQs before playing games now? The JP+ skill unlocks at job level 10 (so lestatdark got exposed for FAQ looking), so right after the stupidly high increase for job points needed for the next level. That basically rules out getting the skill early, unless you want to do some insane grinding. I think that's a total of 6,000 JP and it takes a while before you get 20+ from regular battles.
I maintain that there should be much more slots for support skills, because that way picking the wrong jobs wouldn't feel like such a waste of time as you could add minor stuff like Defense +10% to get a bit more powerful.