piping
You are making it more and more complicated. If the tub and sinks are going to be nearby, then install a 3" combo on its back at the sink location. In the riser insert a 3x3x3x2 side inlet tee, (left or right inlet depending on which will orient better for the next step). Angle the 3" side inlet towards the toilet and run a pipe to the toilet location. Use fittings to direct the 2" inlet to the tub's "P" trap location and install a pipe, (up to 48" or 60" depending on your code) with the P trap on the end. Continue up with 3" cleanout and a 3x2 bushing in it. Then install the 2x2x1 1/2x1 1/2 double fixture fitting for the two sinks. Insert a 3x2 bushing in the end of the horizontal 3" combo and run a 2" pipe to the shower. Then either continue to the "P" trap with a combo, (and possibly a cleanout in the vertical pipe), for a vent, or use a long sweep 1/4 bend with a tee above it which can be rotated to line up with the shower opening and then continue the vent, again with a cleanout, up through the roor or to the other vent. This all depends on the distances involved, but some variation of this will fit your installation. For example, you can install the side inlet tee at the shower and angle to the toilet from there with the shower "P" trap connecting to the 2" side inlet.