You can set the option:
<Pack200Effort>0</Pack200Effort>
in your JWrapper XML to disable a lot of the compression in JWrapper. This should speed up both builds and extraction.
Note though that this won't apply to your JREs unless you set the option but also delete the JRE archive from your build folder. JWrapper will then rebuild the JRE archive from scratch using your options which will take some time the first time but subsequent builds and unarchives will be faster.
If you want to use a different build for the trial version you can just use a different jwrapper XML that uses a different build folder (and therefore has a different set of cached JRE archives).