Hm a good idea, this should be really helpful
When making a couple of changes to the menu...ini (the OLCGui and MFD merge-mod) I had a similiar idea, too.
But I only created some java tools to do some vast amounts of changes for me. I stopped there because I just tailored those tools for my specific needs, but there are in fact some things a tool can help with when editing this (bloated) ini-file.
The things I created those tools where:
1. renumber all items in a specific section from a specific point onwards to a final point
(say, make [G3F I200]->[G3F I265], [G3F I201]->[G3F I266], ...) This saved me a lot of manual editing.
2. scan for all ParentIDs in a specific section and look whether the matching ItemIDs are also there (makes it easier to point out some errors sometimes)
Those things can be useful too when editing some complex menu...ini.
Maybe for some future enhancements of your tool ?