I recognize I'm a noob with this & still feeling my way around.
And ironically the layout was designed by a pro who's no longer in the picture. The bath/shower as interchanging vents was his idea & I can't see any reason why it wouldn't work.
I'm thinking the same can be done with the 2 sinks, a trap on each, upstream of the junction in the vanity. But if not it's easy enough to vent into the wall right there instead.
I assume I'm putting vents in the walls behind the toilet & the sewage well too.
Here's a better picture -