In general I’m against any microtransactions. I much more prefer normal expansions that were released for AoE series - from Rise of Rome to African Royals.
But if having a different support strategy, with smaller content patches like new maps, single civs without campaigns or single historical missions means that is not viable - then yes, cosmetics is THE best place to include microtransactions.
It still would be nice to have a way to earn at least some of them, for dedicated fans, but these are things not related to gameplay so ultimately it doesn’t matter that much. As long as default skins are not terrible- no reason to be outraged like with paid maps splitting the community or even worse - paid gameplay features.
Having to pay to unlock player color changer or treaty option in skirmish is a nightmare scenario.
It’s hard to come up with a modern monetization strategy for a classic RTS game like AoE. I think expansions work fine for them, but also I imagine they have bigger expectations than ones for 2DE and 3DE.
I’ve posted pics of, I think, first skins in AoE series, outside of cosmetics in AoE Online and (recent) event mods in AoE2:DE:
Could something like that be charged for? Well, it wouldn’t be the end of the world. As long as normal skins looks good, and new ones don’t give gameplay advantage or look like crap (with some RGB flashing colours etc lol) I guess it’s ok.
It would be a bummer to haviing stock crossbowman skin and paid, cool skin oif much more detailed verison from some Italian kingdom, but hey as I’ve said- maybe they could tie it with event and challenges. Just like USA civ that was free for people that completed event goals.