AgreedSo on underslab work, running drains under bearing walls is obviously to be avoided, as they'd be in the footing, but for non-bearing walls, there's no reason not to do it?
That would make dry venting the shower and WC easy, just put a san-tee under the wall, and the drain drops down into a combo on the building drain. The shower san-tee can be in a corner so that the vent avoids the valve area. The WC could still be wet vented if preferred.
Or if the building drain can't be under the wall for some reason, the shower could be dry-vented via a san-tee under the wall next to the entry to the shower.