MouseControl was finally updated to v2.0. I had to make it unlisted because I could not get it approved on addons.mozilla.org for public listing due to its power.
Please go to the release page and follow instructions - https://github.com/Noitidart/MouseControl/releases/tag/v2.0-unlisted
- Perfectly cross-platform (Windows/Mac/Linux)
- Allows more then just the standard three mouse buttons