A lot of the arguments levied at the OP, assume that abilities wouldnt be scaled down in enmity, potency, etc while sync'd.

I have actually seen this argument before a few times, and its always this same thing that gets brought up at the reason why it cant. But really it could, it would take a lot of balancing though on SE's part and I feel like THAT is more likely the reason we dont see it. They dont have time to rebalance things at every possible dungeon lvl to make sure it would be in accepted norm's. So while the actions could be tweaked for level sync, it would likely be far too time consuming to do it for every job.
(But man would I love to see it!)