Russ,
I hate to disagree, but I stand by my statement - there are only 2 paint or coating (if you prefer) types: lacquer and enamel, and it's based on the how a particular resin drys or cures, nothing else. It doesn't matter whether we're talking about paint types inside or outside the paint industry, it's all the same. I think we need to get rid of the concept that paints are different inside and outside of the industry, especially when so many modelers use automotive paints that come in the same variety of flavors, i.e., lacquer, enamel, acrylic lacquer, acrylic enamel... It can lead to a great deal of confusion. After all, where do paints come from? The paint industry. They're all subject to the same or similar development. And I'm not sure about the point you're trying to make by saying that "lacquer is not paint", but please check the definition of the word. It's accepted in the industry (and by everyone I know) that if we're talking about paint, lacquer is paint (please check the definition of "paint" as well).
Regarding acrylic's, even though the term "acrylic" has become generic outside the paint industry, it doesn't change the fact that it's still considered an additive that's been used since, IIRC, the 1950's. It's nothing new outside of the hobby and I know of no one that considers it "specialized". Acrylics are more common now than ever. As with any paints, care should be taken when adding solvents to ensure compatibility.
As to the use of universal solvents, you certainly can use hardware store lacquer thinners, mineral spirts, and alcohols for thinning, but be careful. The results may not meet your expectations (if they do great!). The only thing I use hardware store solvents for is cleaning. Solvents for thinning or reducing paints come from a paint jobber, and the results can be significant.
Finally, you state that, "...enamels and acrylics, which form coatings by polymerization processes..." - what about acrylic lacquers? Not all coatings that contain an acrylic component are enamels. Can you identify which hobby paints are acrylic enamels and which are acrylic lacquers? Not always. If anyone read that statement closely, they would be lead to believe that all acrylic paints are enamels. This is a good example of a statement that can lead to confusion.
I've tried to help people with paint problems by understanding the realities of paint based on facts. I've worked with paint application for many years, and side-by-side with reps from paint manufacturers. I do know something about paint, that being, hobby and non-hobby paints are still paints. Same rules apply.
Klaus