In the Seanchan absolutist system, the consort is just a consort. There's no question of Mat being Emperor. He's just the Empress's husband. He stands with the Imperial family in rank, and above all the High Lords and Ladies (like Tuon did when not under the veil), but it's still a very very long way from where Tuon now stands.

Not that I see Rand formally serving Mat anymore than Tuon, really!

I think Jordan's point is precisely that all these conflicts of hierarchy.. should the Dragon outrank Amyrlin and Empress and vice-versa are completely counterproductive and futile and even sheer lunacy considering what the world faces. All the characters have to sit on their prerogatives and honors and understand they're all standing equally in the same mess. Rand isn't supposed to have the whole world kissing his feet and venerating him as the Light made flesh, and neither Egwene nor Tuon are supposed to "control the Dragon". The Wheel is the one pulling Rand, not Egwene and Tuon, and Rand isn't weaving the Pattern either, even though by TGS he often acted as if he thought he could bend the pattern to his will. Who thinks he turns the Wheel of Time might learn the truth too late. It's true for all of them.