This seems a bit of a knee-jerk reaction, so I wonder what's fueling your ire? I mean a JRM Cup team doesn't even exist, so nobody knows how it would be set up, who exactly would own it, etc.
I for one feel the rules interpretation for Hamlin was (is) completely sound. Denny was permitted to drive for a four-car team *plus* own another team because there is no evidence that 23XI operates for the benefit of Joe Gibbs Racing. All they do is pay for technical services rendered, same as many other Nascar teams.
Sure, it was a rule modification... so what?