I have actually done this more than once. It works but you can end up with a few rough edges if you remove the Manjaro specific stuff. Nothing serious.
If you want to make the switch completely, there are quite a few steps: https://forum.endeavouros.com/t/howto-convert-manjaro-to-endeavouros/5954/97
One thing I am curious about is what happens if you just add the EOS repos to Manjaro.
My biggest gripe with Manjaro is the way they hold packages back and the issues that causes with the AUR. If you had both, I imagine you would mostly just get the EOS packages for anything that was not Manjaro specific. If you also migrate the kernel to an EOS ( actually Arch ) package, most of the Manjaro damage would be contained.
Adding the eos-hooks package would make it report as EOS as well.
I might just give it a shot just to see what happens.
As a fellow poor communicator, I just want to say that I appreciate your self-awareness.