honestly the heavy weight mechanic 1. just makes sense and 2. makes the character feel more unique than it already does, which is certainly saying something about the uniqueness of the character
anyway, with that, here are my general thoughts on the character:
i like milne a lot, she has a very instinctive playstyle, which somehow fits in a game like srb2 which sometimes requires you to plan your moves ahead so you don't get screwed over by the thok or the spin, or even an unlucky bounce. i also really like milne's crystal toss ability, which is a great projectile, but honestly could go a bit faster? i've often found myself missing shots bc they were barely too slow, but otherwise are a pretty good projectile, even if i didn't find myself using them all of the time.
star of the show though is the double thok, this is just great to use, it adds a bit more mobility to a heavy character and also an offensive melee move, which is pretty neat.
the other abilities (passive or just very case sensitive) are just okay in my opinion. the ability to run through spikes is nice, though i have only found it useful in the metal sonic race, since other than that the areas in which i should be using it i either forget or just can't get enough speed. though i will say it's nice that it applies to the thok as well. the enemy throwing...in theory it's good, and when you get to actually pick up and throw them, it's cool, but the activation box is just way too small for it to be useful, even when i'm using the milne and fang combo. in that situation i just end up giving fang a shield several times over.
other than my criticisms, it's a great character, a delight to play as for the most part, a solid 7.5/10