I've been trying to get an effect similar to the velvety matte quality of gouache or poster paint on parts of my canvases. No matte mediums I know of approach this quality.
We do have a couple of product lines offering the qualities you desire. High Load Acrylics (HLA) are a paint line based upon the gesso formula. They are loaded higher than our Heavy Body or Fluid Acrylics and the result is qualities similar to the gesso in appearance. They are richly pigmented and are not tints with white, but strong, clean paints. The range of color is limited to earth colors and other inorganic pigments for the most part, but we have worked on creating another line of paints to fill those voids in the palette.

The Matte Fluid Line, which was developed as a custom line for one of our customers (just like the manner described in the most recent Just Paint). They had tried the HLAs, but needed more colors. We created a formula, which was thicker than the Fluids, and more opaque, but had greater leveling ability and offered a smooth matte sheen.

We also have Super Loaded matte Medium. As you mention, most other matte mediums fall short of achieving a matte finish, and when blended with other glossier products, result in more of a semi-gloss than matte. SLMM has about 3 times the matting agent of regular Matte Medium and will make glossier products matte.

I would like to coat Strathmore illustration board (which is acid free) with 2 coats of Gesso without sanding and draw my illustration on it using a 3B pencil and then do a watercolor painting on it (wiping out areas and possibly scratching out areas of white). If it were to my liking I would like to use it as a watercolor painting. I would like to coat the watercolor painting with three coats of Matte Medium and let it dry for 24 hours and then paint with oil paint on top. Could this be considered archival quality?
Although there is some speculation about oil paints being applied over acrylics because they are such different materials, we have not seen any evidence to support a problem. However, to err on the safe side, we do recommend using toothy, matte and possibly absorbent acrylics to increase the adhesion. In your case, the Matte Medium should be sufficient, however, allow these layers to cure completely before proceeding with oils. The rules for oil painting (i.e., fat over lean) still apply.