It's still never really been stated that jobs will be completely locked to certain stuff. Yes they'll be locked with certain types of armour or weaponry, but that's not really any different to what it is at the moment anyways, you can't be an archer with a sword, because that makes you a Gladiator.

As for skills, I doubt they'll prevent players from adding skills that aren't relevant to a job/role, so you'll probably still be able to equip Fire II if you're a Paladin or Cure II if you're a Thief. You're still as customisable as you were before, but your role in battle has a more defined purpose. Jobs will probably just add extra mechanics ontop of what we already have as classes, so for instance a Thief will gain poisoned weapons, DoT's or (dare I say it) combo points. you're still essentially a Pugilist, or whatever a Thief is the class defined job of, but with pink frills and extra bling.