Well the thing is we're already screwing with the storyline just being in the past with Wings of the Goddess, according to some of the missions things have already changed from the way they were supposed to end up. I can see them adding it to Dynamis because we've already introduced Blue Mage, Corsair and Puppetmaster to the Crystal War.
To me it just seems the best answer, if they added it to something new they'd need to add stuff for non COR/BLU/PUP else you'd only have those 3 jobs wanting to do it, which doesn't really help much. And I don't see it being easier or quicker(depending on job) to obtain then normal relic gear. If they added ToAU jobs to Dynamis it'd get more people, and they said they've been planning to drop hourglass prices, maybe do that alongside this update, and with the WotG expansion I can see SE going that route, time paradoxes are a tricky thing.