I don't want to use 'Win10PE'. I never told for using 'Win10PE'.... I want to just add/integrate 'Wow64' feature within 'Image Index: 2' of 64-bit 'boot.wim' of 'Win8.1U1/Win10'.
Mate, boot.wim of Win10 is essentially a pre-installation environment ( PE ). There is nothing wrong in calling it as "Win10 PE".