Played around with some things.
Changed all the xcopys to copy-item because powershell sometimes ran it in the PS window, and sometimes spun up external CMD windows leading to out of order execution.
Same with the attrib.
I believe this should work still on all the versions but I haven't tested them.
Was trying to figure out what the mercs 1.1 patch did/changed.
It's a finicky bitch and I got bored.
Since it's not being installed, I removed it.
If you want to play around and figure it out, there's a couple of PS scripts attached that can create hashes for a directory tree, and then compare the stored versions to the current.
Updated installer file 15/02/24 (added more editions)