Actually like Smash Bros. Monster Hunter uses additional system resources. This means you can't launch the web browser, so spider3DStools is out of the question.
Care to elaborate? There's a huge difference between using the browser to boot a game, and attempting to interrupt the game to view and modify RAM on-the-fly via the browser. The former is used before the game calls the extra system resources, the latter after. Which modified regionthree are you talking about? It's my understanding that you can't boot Majora's Mask (and I assume MH4U) using regionthree.
MM3D will boot via RegionThree, you just can't run it across regions because the game looks for language files from its region. This "modified RegionThree" does not yet exist, but it very possible to create. What it would do is write a code handler to some free RAM, then inject code into the game's main executable during launch to call that code handler.
