You could buy the Hydroban drain, or the Schluter Kerdi conversion drain, build your single layer of sloped pan, and then cover it with your choice of sheet membranes, or go with a Noble drain - they're all good. All of those have a wide flange designed to accept surface waterproofing, a clamping drain is designed to accept a vinyl liner. Just simply putting in the bolts of the clamping drain can be problematic keeping the waterproofing if you use liquid waterproofing materials.
Deckmud is NOT really strong stuff...it's great in compression, but it is mostly sand with enough cement to hold it together...it NEEDS to be porous, at least when used in a conventional mudbed shower, and more cement or more water can cause it to shrink and crack, neither of which is a good thing. In the right mixture, it does pack easily and can be shaped. So, depending on the manufacturer of deckmud you buy (assuming you buy it premixed, and even if you don't, you should consider their guidance on the premixed stuff along with the industry), over a wooden subfloor, it needs thickness and lath to provide the strength. Silicon in the seams of the ply is not called out in any of the industry specs for installations of tile over plywood. Some CBU (cement backer unit - aka cement board) call for it, most don't, the plywood industry doesn't spec it. The thinset manufactures don't spec it. Do it if it makes you feel better, just don't get sloppy, since thinset won't stick to it. Any that gets into the seams will end up getting crushed over time to a powder...not a big deal - there's always a little bit of air space in mortar when you mix it (called entrained air), so there's space. And, once the plywood is acclimated to the room, and you don't get it wet, the plywood industry calls for there to not be any gaps when installing the underlayment ply! THey require it on the subflooring, since the house can be open to the weather, but once closed in, and conditioned, once acclimated, the underlayment can be tight...most still leave a gap, but look at all of the vinyl installs...they purposely put filler in there to hide the seams and you do NOT see the vinyl puckering or lifting at those seams for a reason...once acclimated to the room, it is not going to get rained on or snow sitting there, and the moisture content will stay reasonably consistent. There's a BIG difference between rough-in of a house with moisture and expansion/contraction, and a finished surface done to a completed house.