I had a look how a few different groups set up their openers, back during the thread discussing the role of Plunge in DRK's opener. I noticed that a certain world-first progression group was doing exactly that on A5S-A7S, except with Grit on for the initial PS. It's going to be partly contingent on both you and your ninja, but it seems reasonably doable, even when playing with highly skilled and geared dps.

I don't really see the point in using Shadewalker on WAR during an Unchained opener. If anyone else is remotely close in enmity after that opener, your WAR really should reconsider their job choice. If you're going to swap in the first two minutes or so, you want that difference to be applied between your DRK and your WAR, not just between your tanks and the rest of the group.