Idea is for the main unit to handle Left, Right, Center, Sub while another WiiM handle the rest of channels.
Isn't that just what the current 5.1 is doing?
Or are you talking about more channels? Cause I could see that being done the same way as currently, though probably with a stronger processor or some other problems.
For example a "Wiim mega ultra super" for the front, center and sub. (would be cool if it had two sub outputs) With HDMI eARC, and HDMI passthrough for consoles, blueray players, streamers etc.
Then you could have a Wiim amp or something driving the rear channels and two or more Wiim sounds for the surrounds, or even use multiple amps with assignable speaker outputs. (for example you could set one to play the left rear and left surround, then the other for right rear and right surround, or you could have one for rears and one for surround)
That could in turn allow them to make wall / ceiling mounts for the sounds, so they can be used as height channels.
Though all of that would only be possible if the main unit was able to process and send out the signal, and everything worked wirelessly without any problems.