I would fix them like this:
-Man at arm upgrade removed, Militia is instantly upgraded to MAA for free upon aging up.
-Base speed increased to 1.0 (equal to spear line).
-Squire: move to feudal age, costs 75 food.
-Supply: -10 food / -5 gold cost for militia line. Plus cuts infantry’s population cost by 25% (4 infantry units = 3 pop)
-Gambeson: +1m/+1p armor.
I would save it for civ bonus. As a base line unit, making it Karambit mass spammy isnt making this unit helpful rather other way around. You dont waste your training time for nothing. Having Obuch Stats without gimmick is actually helpful or taking the treatment from AOM by making Swordsman like infantry in general a soft counter to Cavalry.
The fix is to make MaA absurdly broken, I understand.
If you’re going to propose such a thing, you should at least say how to rebalance the key civilisations.
One alternative can be done is through taking too long to create M@A at Dark Age. Perhaps double the creation time. But once its upgraded to M@A automatically in Feudal then you can create it how you were used to. But a radical early game change regardless. It can either decline of M@A opening or might turn out to be OP. Basically you are taking the time to create 6 militia in Dark Age for 3 Militia opening.
Again creation time can take long enough while opponent already reaches Feudal Age at that point. If possible 2.5x time in Dark Age can still delay the rush by large margin. Just making 3 Militia can simply take more time than to research Feudal.
Because the unit is already cost-effective against many units in melee, but has the problem that the situation rarely occurs.
So raising the stats without raising the cost would make it too strong in some situations. While maintaining the same cost-efficiency and raising pop-efficiency in the meantime, makes the unit generally easier to use.