Yes you may.
With-in the boot.wim or boot_x64.wim files you will want to edit the startnet.cmd files to include any custom scripts that you want to call pre-provisioning login. You will want to download the Microsoft ADK for the correct version of winpe the wim files contains if you want to inject anything via dism (drivers, updates, modules, etc), but if all that you want to do is edit existing scripts and add scripts to it - then any version of dism will work for this task.
Refer to here on examples of how to mount a wim to edit its files:
Refer to here on how to add custom scripts to the wim:
Hope this helps,