Having seen PNB's Midsummer on Sunday (will write up my review tomorrow), I walked home wondering "why isn't MCB doing this very Balanchine ballet? they could easily rent the sets from Pennsylvania Ballet or Boston Ballet". They could also do the Balanchine Coppelia.
But to echo Christian's point, that wouldn't be very "Morphoses" of Madame Lopez. If they can rent ABT's sets, then surely they can rent sets for a Balanchine full-night story ballet.
Without knowing much about the Miami City school, I'd wonder if they had the kid population for these two works -- they both require a fairly large corps of kid performers.
Nonetheless, I do think that some of the Balanchine program-length works are becoming the same kind of milestone ballets (we do them to prove that we can) that the Petipa warhorses have been.
(looking forward to hearing about your Sunday experience -- I couldn't go to that performance!)