unless games that used mii's in games would not even boot at all or crashed that would be a big problem and they could not release such a solution
this is my guess and that it was also very unstable but i still think it exists and i think it would be possible to use if only once to install Mset then switch the launcher to 3.2.1 , unless they are working on building a unified launcher that can work with miimaker to install Mset and then work like normal 3.2.1 after mset is installed , they got the Mset from the scene and only recently so maybe they have not yet fully explored this possibility yet