Well, I imagine that (most of) the people in favor of cosmetics aren't aiming to make Bannerlord resemble TF2. Surely the skins could match the style and tone of the default designs.
One potential issue I could see with this, however, is that it may become more difficult to distinguish weapons or classes from one another.
As for the broader discussion of the mean green, that almighty dollar, I think it wouldn't hurt to have purchaseable cosmetics that can be earned in a reasonable time-frame through playing the game.