The build is totally made from scratch, no prestored install.wim / boot.wim, no prestored "base win7pe package").
Overall time until starting VirtualBox is 4 minutes 15 seconds.
RamLog.gif 219.55KB 67 downloads
RamSystem.gif 76KB 63 downloads
For those who wand to know how that result can be achieved (and who want to check that it is not a fake) attached the log.
EDIT: To compare: The same project built in the classic way needs about 11 minutes.