Epoxy coated slab on grade 1

Don't you want horizontal movement at your construction joint? If yes, then keep the dowel detail at the construction joint. If not, then you should develop the SOG reinforcement on both sides and provide a keyed pour stop. Typically, I locate/consider construction joints as control joints and detail them for horizontal volume change with a tooled edge and flexible sealant to bridge the expected gap.

Do not put traffic membranes on at-grade slabs. It won't allow vapor to pass up from the ground.

"It is imperative Cunth doesn't get his hands on those codes."

I am assuming this is a thick epoxy coating and the plate dowels are in control joints. These coating can be pretty thick and some mimic terrazzo. I would contact the coating manufacture (or their rep) for recommendation. If they are a quality manufacture, they have experience with these situations and have a vested interest in providing a good looking and long lasting coating.

You will not prevent horizontal movement of a slab! You can epoxy coat the slab, just make sure you have joint the coating to match the slab. If you coat across the joints, you will get separation of the epoxy. Whether you use plate dowels or bar dowels doesn't matter....neither is designed to inhibit horizontal movement. If they did, you would have cracking!

To add to what MacGruber22 pointed out:

An epoxy coating atop the slab would act as a vapor barrier which can be problematic. Furthermore, the epoxy coating has to be able to contend with the high pH of the concrete. The master of such knowledge is Joseph Lstiburek. His books on the design of building envelopes have earned a permanent spot on my shelf. I have learned so much about insulation, moisture control layers, vapor control layers, air control layers and drainage planes, and where they should be placed around and on which side of structure from his books.

Here is an older article by him specifically on slabs-on-grade. He discusses vapor barriers and epoxy top coatings.

Concrete Floor Problems -- Joseph Lstiburek

Epoxy coatings are routinely used on concrete slabs. Lstiburek is knowledgeable and has some good information, but it doesn't apply to all cases. With slabs on grade and moisture migration, each must be treated individually.

The high pH of the concrete is also something that can be covered by proper selection of the epoxy and proper preparation of the floor slab surface prior to application.