Bringing Up Baby is one of my faves! Your analysis of the David/Susan Luke/Lorelai parallels is great.
Now, if you're able to see Christopher and Lorelai as the meant to be true love couple in GG, you could see a Philadelphia Story thing with Lorelai as the rich girl in denial (Katherine Hepburn), Christopher as the former love who knows her so well, Luke as the attractive temptation, able to keep up with her to a certain extent and clearly attracted to her, but a good guy in the end who won't take advantage (Jimmy Stewart), and Max, maybe, as the bland clueless guy she is planning to marry but who clearly doesn't really get her and is kind of condescending (whoever the actor was who played the boring guy).
I think I've wandered more into fan fic realm than an intelligent discussion of L and L... but speaking of fanfic, I think I read a Rory centric one sometime in the past few months where Rory is set to marry a bland Dean (they got together later than in the show I think...), Logan as the Jimmy Stewart reporter brought in to cover the socialite wedding, and Jess as the Cary Grant ex who knows her so well... forget if it was finished and other details, will see if I can find it again....