Unless it’s the other way around, which I think is actually more likely. the boss (ms) has the idea to sell skins, and the devs have to really do the work of figuring out how much work each optimization strategy would require and if that/those strategies would yield sufficient performance improvements.
I suspect this hasn’t been thought thru very deeply, and not as a dig to the devs. in 2018-2019, when they were working on DE, they didn’t NEED individual civ unit skins. so anything to facilitate that would be an extra investment but yield no additional return. you couldn’t sell DE for more cause it had all the extra skins IMO. so that’s all the further you need to investigate. Nearly any substantial effort would exceed it’s value, so no need to accurately quantify that additional substantial effort.
but NOW when MS is looking for additional ways to monetize aoe2, now there is a potential to make money off of skins. so now there is potential that the effort to facilitate regional skins could be low enough relative to the potential returns. But the only way to know is to actually do the work in estimating the performance increases and the effort required.