You want Endeavor, who is owned by Delta and who Delta has complete power over, to kick Delta's butt? That's not going to end well. If Delta's pilots want Delta's butt kicked, they're in a much better position to do it themselves rather than outsourcing it to the regional.

Whether Endeavor takes this or not has absolutely no bearing on the scope. Delta wants it, and Delta thinks they have an existing contractual right to it. You're more than entitled to fight that, and I hope you do and I hope you win. But if you don't, then don't blame Endeavor pilots for wanting to take advantage of some benefits that the Delta contract allows, as ruled by an arbitrator, rather than let them potentially go to someone else.