Here's a little something, the reason equips are banned is because altering your stats in any way is not legal in tournament play. Mii fighters just like the rest of the cast come with a default weight, height, hitboxes and hurtbox, atk, def, speed, jump height, running speed, air mobility etc. that is included within the game with the guest miis the game brings by default. Altering any of those stats in any way is the equivalent to using equips and therefore should be banned. Not only that but in their case to do so they have to use a method OUTSIDE the game, so it is in fact something that's not part of the game.
So swordfighter wants less ending lag on his attacks and the others want more mobility, meanwhile chars like ganon could use at least 10 points in speed which is barely noticeable all around but allows him to do autocancel short hop dair and marth could use a smooth lander to patch up that landing lag on his aerials, but we don't allow that because its an equip, well with the H/W on miis is the same thing the only diference is the method used to alter those stats is the mii maker, which is even worst cause to do it you have to use an option that is not included within the game and changes more than just their speed, power and defense since it changes their hurtbox and hitboxes as well as other things.
Bottom line, modifying your stats in any way IS NOT ALLOWED in tournament play and that includes both equips and changing your height and weight.