If it is only going to be booted once to partition and format, why is boot speed an issue?
Save remastering time and trouble by having a tce directory on the USB stick with needed extensions.
Its will move around and boot on different computers for bringing them to life.
Remastering isnt much work really.. I use root access on a separate debian computer, extract the core, add the tce files and auto generates the Onboot file from whatever is loaded into tce/optional, repairs owner/group/mod and cpio's and gzip's it to a new corefile. It mostly done in a script, so its not much work, and it happens quickly.