you don't need a plugin to do that
create a batch that exports the registry you want to save and then create a second batch that imports those patches again after boot.
To do that effectively you need a startup batch that scans for the place you used to store the exports.
You could use a tag-file on a local disk for that for example ...
If you are interested in a BartPE that does not need a ramdrive have a look at my site http://sanbarrow.com/phpBB2/viewtopic.php?t=1544
A BartPE like I use it uses a USB-disk, USB-stick , Truecrypt-container or VMDK instead of a ramdrive - in such an environment doing the export at shutdown and import at boot is very easy to acchieve