Some tweaks to cards and techs would go a long way:
Jesuit Influence - Move it back to age 1. The strategies that caused this to be nerfed aren’t really an issue anymore.
10 Desert Archers - Replace with Maya Archers that also buffs the Desert Archers. This would give a reasonably reliable light infantry option no matter what age up you went with.
Goa Followership (Indian Alliance) - Sends a Villager and a Cow with each shipment. That would give an actual reason to age up with India and provide an alternative to shipping or buying cows.
There could be some alterations to different age ups to make them more viable. Maybe the Conquistadors from the Jesuit age up could be reworked to be more like Rifle Riders and supplement the lack of light infantry. That would have to consider the ramifications to other civs, but it could make the unit in general a lot more interesting.
Fixing general African stuff like how tedious Farms are would greatly help Ethiopia as well as Hausa.
Most of the other issues stem from how MM are just so much worse than Universities in all respects. They’re temporary instead of permanent, you give up coin for the influence, they are a rip off when using Kingdom Builders, and they run out at the worst time. There are certainly things that could be done to make them a bit more user friendly like a recharge button, but that feels like just as much of an exploit as smashing and rebuilding them. I made a post contemplating Church Forests as a hypothetical alternative, but something like that could really fix most of Ethiopia’s issues. It would change up how they’re played quite a bit by giving them a very reliable source of wood without necessarily needing to go out to chop, but that could also be a very interesting play style. The whole building on a mine thing would fit a lot better for a Malian/Mandinka civ.