Beware of long legs…
I voted for short legs, by the way. But I am just as open to the idea of the Matoran being the same height as the Toa. This is me trying to play devil’s advocate.
My suggestion for an approach towards designing the Matoran is to make it clear they have different priorities in comparison to the Toa. Instead of trying to come up with a catch-all look, the Matoran could have slightly more unique designs depending on the environment. Matoran can be soldiers (like the two to the left here), merchants, fishermen, tailors, etc (Costume design instead of creature design). In other words, what would a cook look like in comparison to Iron Man?
Here, the soldiers are wearing armor that’s visibly worn out, mostly colorless, and less detailed than Tahu’s body. Not all Matoran have to be that way, but they’d clearly not be the ones going out on adventures. Narmoto and Jaller are elaborations on the base Matoran. Still a little bland in terms of color scheme, but clearly a little more important. A way of showing that “special” Matoran can still look less powerful than a Toa.
If it’s worth avoiding the legs discussion, these ideas could still maybe work with Hobbit legs. Please don’t kill me.