Windows installation media should be more transparent and work without bcd patching.
I was not able to make standard operationsystem/windows.rb model work with PXEFILES = {:kernel => "startrom.0", :initrd => "boot.sdi"}.

I propose

PXEFILES = {:kernel => "wimboot", :initrd => "bootmgr", :bcd => "bcd", :bootsdi => "boot.sdi", :bootwim => "boot.wim"}

as well as changing the pxe_prefix to:

def pxe_prefix(arch)
    "boot/windows-#{arch}/".gsub(" ","-")
end

because windows requires all boot files to be in one directory.

This features should be combined with a small foreman-proxy change.

This can be combined with my effort of elaborating windows prep for provisioning via foreman (https://github.com/kireevco/wimaging)