I would recommend to just use any of the Git GUI clients rather than a plugin for Word.
I'd recommend GitKraken. A note, I do use GIT for software development with tools that do support git natively (VS Code) and I still prefer to use GitKraken for handling commits, branches and push requests as it is a dedicated product focused on doing a single thing very well.
I'm not sure what your intent for using GIT is but, as you note, you'll lose most of the useful features that come from using a distributed source control system and I honestly think there are way better tools for this, including some from Microsoft.
- Use the version history option from Microsoft One Drive. This comes as a given with every Office 365 subscription and it allows you to keep using word.
- Consider switching to Scrivener. It's a dedicated tool oriented towards writing with a price point that makes it a silly buy and it does have a revision control that is specifically tailored to the writing and editing process and is broken down into two parts:
- You can take a snapshot of your document state at any point and later on come back or compare to that point in time (that would be the equivalente of check-in).
- You can also go into revision mode which will track in a different colour the changes you make while on that mode (although I must admit I find this one less useful)
- Consider switching to Ulysses. I actually love version history on Ulysses, you just take a document and hit Version History and it will allow you to go back on all snapshots taken automatically, neatly organised by date and time and compare that to the current document.
Finally, if you don't want any of those options I'd also suggest using Markdown with VSCode and GIT. In that environment you'll get, for free, all the good options integrated inside VS Code and the ability to export to Word at a later time.