I ADORE the funny and smart Rachel Dratch, and I'd love to see her star in a TV show. But 30 Rock... I cannot imagine with her in actor role (even one designed for her rather than Jane)... an *enormous* part of what makes 30 Rock work and the humor of it is Jenna as written for and played pitch-perfectly by Jane Krakowski.
While I was sad to hear it shook out this way when the show began, I think the show I love so much would be massive different if it had not been re-developed as a standard single-cam and with a new Jenna. She is 1/4 of the show really.