...or, more to the point, something where Xenos races are the highlighted protagonists and the Imperium is either the bad guy or in the middle. How interesting would that be to have, for instance, an Eldar campaign against Chaos on or near an Imperial World? Or a Tau Warband having to fight and survive their way through a system in the middle of a war between Orks and Guard?
I think there would be a good response from Xenos players excited about being the focus of a campaign and there will rarely be a shortage of Imperial opponents...