Awesome. I doubt Mueller takes up the invitation, and CNN will dismiss Rich as the leaker by making the story about "claims Rich was murdered on Clinton's orders."
It brings Clinton and her criminality back into the mix. It also brings in all the corruption exposed in the emails. Low hanging fruit for future tweets putting political careers and lobbying efforts in jeopardy.
If Mueller completely ignores the Seth Rich death in all this we will know who he is and who he works for real quick.