As a Fedora packager, I would wholeheartedly +1 a move from the current "biarch" setup to Debian's multiarch setup. I believe the ARM architecture is doing something similar to Debian here.
As for the Debian/Fedora split, there already was one since 64bit uses /usr/lib64 on Fedora and /usr/lib on Debian. So it's that they ever agreed 100% before anyways. (I do prefer /usr/lib64 and /usr/lib split for 64bit over Debian's previous "native == /usr/lib" setup which makes installing 32bit on a 64bit flavor easy, but multiarch is a better overall solution).