You should post your question only once. Not both here and
I expect it would be very complex to merge the right things from 32 bit and 64 bit Red Hat to construct a system that would work with either kernel. Probably some of the startup scripts would also need tweaking to make some of the startup steps conditional on which kernel is booted.
Linux is pretty good about supporting both 32 bit and 64 bit versions of the same .so files in one multi-lib environment. But there is no similar structure for two versions of the same binaries.
64 bit Linux uses almost entirely 64 bit binaries, none of which will work with a 32 bit kernel. Most of the 32 bit binaries will work fine with a 64 bit kernel, so the "merged" 32 and 64 bit distribution would want to use mainly 32 bit binaries.
I'm not really certain, but I think there would be several 64 bit binaries that you need or want anyway and those would conflict with the names of 32 bit binaries needed with the 32 bit kernel.
So I think you would need to create a /bin64, /sbin64 and /usr/bin64 and move some 64 bit binaries there from /bin, /sbin and /usr/bin and also adjust some scripts so paths are set to search the 64 bit directories first when a 64 bit kernel is booted and not search them when a 32 bit kernel is booted.