Thanks for the info. I personally only use x64 original MSDN ISOs that I get from torrents and file-sharing sites, then compare the hash against what is on MSDN. Windows installed from MSDN sources are generally not already activated, so they either have to provide their own key or activate another way (how they go about that, I could care less). I have rarely had to install x86 Windows for anyone, nearly everyone I know has x64-capable hardware, but if I do then I just create a standalone USB drive for that install. I assume that the x86 instructions you're giving will work for x64 too. But why, exactly, do you say to use x86? I've always assumed that you need to use an x64 ISO to install an x64 Windows, and an x86 ISO to install an x86 Windows. For installing via command-line I just use 10's WAIK tools, obtained via GetWAIKTools. This one WAIK alone works for everything from Vista to 10 as well as the Server editions.
For splitting WIMs into SWMs I just use WinToolkit, split into 3000MB chunks, with a custom EI.cfg and PID.txt when necessary. That particular chunk size seems to work well, when combined with one or both of the config files.
In the CMD file can I specify an ESD or SWMs, in addition to regular WIMs? XML file? Where are those?
When you mention WinNTSetup, you say you can pick any ISO. But don't you mean imgPTN? In my original I said "I would also need to be able to run the setup in either legacy or BIOS mode". But I meant legacy or UEFI mode.
I don't have much of a use for PEs, except maybe to restore a backup in an emergency or other repairs/maintenance, I much prefer to use the regular Windows setup in combination with ImageX and BCDBoot.
On a side note, do you know how I can get Windows to automatically assign drive letters of my choice, then run an unattend answer file? I have a file called relocate.xml that I use to move C:\Users from C drive to another partition. It also handles the Registry edits. But I would like for this to run automatically during install, or immediately after rebooting into the initial setup wizard. The method I use now involves manually entering Audit Mode during initial setup, then changing drive letters as appropriate, then using CMD to process the script. I found it on TenForums, works quite well as it seems to be officially supported on 10 as of a certain build (cant remember which one), it even survives upgrades, repair install/refresh/reset.