Hi, I have a custom built scripts (I paid a scripter to do it for me) but the workflow is a bit different,
but it works great for my needs.
Basically I do not drop the items i want to rename into it,
I just link them all (we are talking about prims or meshes to be renamed obviously) and i drop the script in the linkset.
Then I get a menu with options to rename, replace or add a particular string to the name(s).
It shows up a preview of the renaming I will get, asking for confirmation.
When done, the script asks if it's good to delete itself. It's really fast, it takes few seconds.
At this point I just unlink them all and they all perfectly renamed without human error.
Big time saver!
Maybe try to ask into a freelancer scripters group.
I'm sure someone is available to create a script fitting your exact needs, for few thousands L$.