another random thinking :
As for the Sidar (semi-immortal promotion) and the Jotnar (ageing), the Maogata seems to rely heavily on upgrading former units and losing an old unit is a bigger loss for them than the usual other civs.
(as you get special promotions from the hunt, you NEED to upgrade those units to a better version as the better version would not have said promotions.)
So : what about a wonder, or a national wonder that works as the former leonardo workshop : can give civ-wide reduction to upgrade costs : -20% (like a small igenuity bonus)
If it is too powerful to be allowed for every civ :
What about a UB for the Maogata (need 4 training yards AND 4 hunter's hall) : give -10% to upgrade cost.
(with 8 cities, one can hope to get -20%, with 12, -30%...Etc ...needs 20 cities to get the equivalent of ingenuity)
The Moagata don't have any weapons promotion..right ?
So why not allow them to still have a way to become better :
I can think of two options :
-use the ageing mechanisme : becoming older, the units becomes smarter : they become more powerful : use some boni less powerful than the jotnar, but still interesting? (immune to FS, +1strength, +20%withdrawal...Etc)
-use the auto-acquire on level : you already proposed it. But I think that what you proposed does not compensate for losing the ability to get weapon promotions : I say that because immune to magic is not really strong for melee combat (save against elemental and holy/death and not even really strong) and removing hell terrain is not a combat bonus.
(well : I haven't played them yet, so maybe I'm wrong) :
What about automatically getting the
strong promotion on level 6 or 8 ? maybe only for the melee line. or
valor ...Etc
EDIT : about siege ... I thought again about it : why not have them be able to build some "Mammoth Herd"... (4
; cost : as a catapult, no upgrade) with ivory and ranger-tech (+ can be upgraded from elephant and mammoth) :
can cast a spell "mad charge" : 15% reduction in nearby city defense,
loses 25% health...
The lore : the Maogata learned how to control and aim the mad charge of wounded Mammoths to lay waste to their ennemy cities, up until the herd becomes too thin and escape the hunter leading them.
Have the "mamoth herd" have -20%heal rate. They cannot be healed unless one takes a Great Healer, in a city with apothecary or a healing potion.
The aim is to make the mad mamoth be only useable 4-5 times to batter the defense until the unit dies.
I propose this as an expendable way to demolish ennemy cultural defense bonus. Thus they have an unique mechanisme.
I thought it might not be too unlore-ish with maogata.