I suspect the "20 kits max per con/year" rule was established as a way to control quality. As you can see, big resin manufacturers like Kotobukiya and Kaiyodo are not bound to such rules, since they have the resources to produce a large quantity of high quality kits. Most, if not all, of these convention-only kits are true garage kits that's usually the labor of love of one person who handles pretty much the whole project from the beginng to the end. Limiting the number of copies that can be sold ensures that the caster won't go crazy making too many kits at the expense of quality, and should the GK turn out to be an embarrassment, the damage done would be minimal. As you know, this rule was established by license holder (e.g. Big West) and not the people who design the products (e.g. sculptors), so the artist's ego does not come into play at all.
Recasting of unavailable products or ones from defunct companies deprives the license holder of potential income from the license holders and the sculptors. The existence of recasts reduces or even eliminates potential interest from third parties to acquire the license to make new kits or reissue long extinct ones. With plans of new kits or reissues scrapped, companies and sculptors have less projects to work on and therefore their future/potential income reduced accordingly. As if that is not bad enough, the kit buying public also loses out because we are deprived of new and exciting kits and potential reissues as well.
I think I heard this whole "public enjoyment" argument during the Napster fiasco, which obviously did not work at court.
Don't care