I imagined this was for events like weddings, gatherings, one-room meetings. I -- personally -- would have wanted a manual flash lighting the room attached high (best) or on a light stand placed inconspicuously. (I keep a weird set of clamps and hardware for this.) I would not want that level to change, although of course throughout the space its level will be different. Then I would try to have my on-camera strobe act as fill to a light that appeared to be ambient but was actually from that "room-bounce" or "room-direct" unit. Having two people able to use that wrap-around light in a neat idea and I hope you can make it work.
I have been avoiding ETTL. Pure fear, lack of experience, I admit! So I cannot tell you if ETTL is retained with one of these splitters.
So this setup is two senders and two receivers. I use Odin, still learning all its capabilities. I think if I were to do this it would require a separate Odin controller, and I never asked what just a controller costs.
Hope you can find a good solution for your particular needs.