Let's see if I can recap slightly differently (expanding on your expansion to make it more clear and to check I have actually understood correctly).
Let's call the DVD "drive L:\" and the EFI Floppy image efisys.bin "M:\".
A DIR /S/B of drive D:\ would be at the very least :
L:\bootmgr <- normal BIOS BOOTMGR
L:\bootmgr.efi <- (64 bit) bootmgr.EFI
L:\boot\bcd <- BIOS BCD
L:\boot\boot.sdi <- Needs to be modified? are two boot.sdi needed? (one for the x64 and one for the x32 boot.wim?)
L:\efi\microsoft\boot\bcd <- EFI BCD
L:\sources\bootx64.wim <- 64 bit boot.wim renamed
L:\sources\bootia32.wim <- 32 bit boot.wim renamed
L:\sources\installx64.wim <- 64 bit install.wim renamed
L:\sources\installia32.wim <- 32 bit install.wim renamed
Whilst a DIR /S/B of the floppy image would be:
No Emulation Bootsector on DVD (embedded efsboot.com)->L:\bootmgr->L:\boot\bcd->Choice between 32 bit and 64 bit
(or can a 32 bit boot.wim be used to install a 64 bit install.wim? )
Please feel free to correct/amend/clear doubt and questions where needed .
Now what is needed is the exact set of commands needed for BCDEDIT to modify both the "BIOS" and the "EFI" BCD's to allow the choices, maybe one could find some clever tricks to "merge" the standard 32 bit and 64 bit BCD's nto oe and then amend change just the file names?
Therefore, someone could write a guide on how to create a CD of Windows PE 5.x 32/64 that boots from any computer with the BIOS/UEFI?
There is NO GUARANTEE whatsoever that anyone will EVER write it, haven't you noticed we are trying to put together the basic method, and you could well at least §@ç#ing TRY to understand what has been posted till now and ask for questions and clarifications about the parts you didn't understand, and try carrying your own experiments INSTEAD of re-asking again the same question.
None of us is contractually engaged (for free) to solve your issue/question, particularly with the artificial limitations that you pose about the "using only MS tools".
As always, remember that it is your question / your problem, and till now you did NOTHING to contribute - even minimally - to this thread (apart re-asking the same questions a few times in slightly different manners).