Sandboxie Support

Actually, there is an alternative. You don't need to mount/unmount reghive, and no renaming which is more efficient that is to create a shorcut to sandbox batch file, you use /hide_window to hide the command prompt. The batch file will start your program and wait for it to finish and do the task/cleaning afterward. The disadvantage is that force program is not applied.

Another option which I'm not sure if will work is to run a batch file unsandboxed. The bach file will start your program with force program in set the program will be sandboxed.
Wait it to finish, mount/unmount reghive then do the other tasked.

Another one is to run batch file unsandboxed then the batch file will start the program in sandbox explicitly, wait it to finish, mount/unmount and etc...

Maybe it's because I'm drunk (my go-to excuse) but I have no idea what you just described. The delete command is working now so I'm happy but I'm still curious. Will re-read tomorrow when sober but chances are I still won't understand :P

Wait so a bat in place of executing the file that does the rest later? Is that what you mean? Makes a bit of sense but why would I try that now that I have what I need via the delete command? What would be the added benefit? Another method, sure, sounds great. You certainly think outside the box!

Its all about efficiency and performance.

Before sandboxie invoked delete command, sandboxie does the phase 1 of delete operation that is:

*Junctions (also known as reparse points) are removed.
*Read-only files and directories are made fully accessible.
*Files and directories that have very long names are renamed to shorter names.
*Renames the sandbox to the format __Delete_(sandbox name)_(some random number)_. For example, if the sandbox is DefaultBox, it could be renamed to __Delete_DefaultBox_01C4012345678912.

The time to finish these operations depend on the files and sub-folders.