Is my plan for an AC disconnect with GFCI appropriate?
I don't like putting the maintenance receptacle on the same circuit as the equipment, especially when you have capacity to do otherwise.
You only need one ground, sized for 40A, so 2@#8, 1@#10, 4@#12 is less than 30% of PVC sch40 fill.
You might be better off eliminating all #12's except the white, upsizing your feeder one size to 60A #6 CU feed to a single outdoor 6 space NEMA 3R panel and using 3 separate breakers rather than mounting a j-box to split the feed or routing feeds through disconnects. Conduit fill will only be 27%.