Well, what's done here (Stan's Theme) is setting up all the variations that happen for each repeat of the theme - adding instruments, removing them, transposing them, and changing them for other instruments. đ
Anyway, here's the first release... Like I said, it's "cooked together" - very quickly done, but seems to leave the MIDIs exactly the same, except for remapping all instrument references.
https://github.com/Jither/iMUSE-Sequencer/releases/tag/Misty-1.0.0
Just decompress the .zip to a folder. The command line provides help (and examples) for each verb (two of them - one for the actual remapping, one for getting the mapping in a more readable format with instrument names). Just type misty or misty help. It then lists the verbs - you can get help for those by typing misty <verbname> help. (Also works to just type misty remap - since it will find that the required input file parameter is missing, so it will show the help for the verb - it doesn't, however, work that way for misty mapinfo - because the mapinfo verb can be called with no parameters).
So, misty remap file.mid is the simplest usage, which will use the default mapping file that's included (the one you sent, but with a single changed line - which allows the mapping info "verb" to find the instrument names). You can create multiple mapping files and specify a different one with -m path-to-file or --mapping path-to-file. After remapping, it outputs to a file with the same name, in the same folder, except for replacing the extension with ".remapped.mid". (Note that it will *not* warn or prompt if the output path already exists - it will just overwrite it). You can also just specify a second file name that it should output to, rather than letting it create a default output path.
ETA: Forgot: Requires .NET 8.0 runtime - https://dotnet.microsoft.com/en-us/download/dotnet/8.0 - the one named ".NET Runtime 8.0.x" will do, but you might as well install the one named ".NET Desktop Runtime 8.0.x" - just adds support for GUI apps (SCUMMRev 8, if it ever appears, will be one of those).