> On an x86_64 system, you can install i686 packages. But then you have already base x86_64 userland packages installed, especially those with shared libs. Additional package installations will cause conflicts with those base-installed packages.
That's just not true.
You can install those just fine ... they won't conflict because the shared libraries go into different directories (lib vs lib64). Which is the whole point of multilib. Binaries in both packages won't conflict either because rpm has a concept of "coloring" which means if you install foo.i686 and foo.x86_64 and both ship /usr/bin/foo it *wont* conflict. /usr/bin/foo will just be the x86_64 one.
Name examples of what you mean. You might just have hit some kind of packing bug for a specific library but they are designed to not conflict and it works fine for me here.