Re Flying boots up to A2 : this is IMHO a very bad decision : to me it's not a balance issue if everyone and his mother gets cheap Flying Boots, it will become one with a mod that restrict them this way..
As a result, only the already-powerful Air nations will have easy access to Flying Boots, letting the other ones on the ground, whereas they're already lacking from less mobility !!!
I'm sad to say that, but it looks like this mod is going overboard : Magic items mod makes useful stuff get nerfed whatever the balance effect is, and practically nothing gets any better.
Yet real balance issues are either not really addressed (ID/AD and Bane Lords still dominate mid-late game, still noone never summons crap-drakes), or even worsened (ah the Vine Ogres are *better* now !! Get the factory rollling !!)..
