I'm going with a single DOT is what we'll have. They love to remove abilities with every expansion. They can claim two abilities at once - 1 DOT and Iron Jaws. IJ would become redundant at that point. Just reapply the single DOT.

Otherwise, I think BRD will get an ability like MCH has: Barrel Stabilizer. Something that bumps up their soul gauge to be used earlier. It can't bring it to 100, that might be a bit OP. But, I could see it going to 50. If not that, then possibly a MNK-like ability akin to Brotherhood. Party attacks something, Soul Gauge goes up.