It could be a mix of both.I'm from when having the best cosmetics also meant you were among the most meritable, powerful, outstanding person within that game, not among the ones with fattest wallets. I guess I'll never get used to how people view skins nowadays.
In Dota 2, and you could buy skins either by paying a lot, or paying minimum and playing good.
I understand some people might be upset by the monetary aspects, but if we want high price pools for aoe2 and better competition (as a result), this could be an effective means.
Of course external sponsorships can also be a way, but even T90 was finding it hard to get sponsorships, inspite of super high viewership (like 30-40K on average?).
There should be some ROI for Microsoft for funding aoe2 tournaments. It can't just be selling copies and DLCs, that can only get you so far.
IMO, the best way to grow the game and scene, would be to cut down the cost of the game, and monetize the skins.
Of course, the units themselves having different skins could be a cause of concern, and might negatively affect player/viewer experience.
But having some amazing skins on castles, universities etc? Would be amazing, as well as historically accurate. There are many glorious castles in history for example, let's have then as paid skins! IT would increase the immersion, hence a plus to the game.