I think this is a fantastic mod and that you've done some really exceptional work, but I have to comment on Scythia. This is with multiplayer balance in mind, obviously, because who cares about being overpowered in singleplayer.
It's pretty widely agreed upon that Scythia is one of the best civs with one of the highest snowballing potentials in the game, to the point she is often banned by larger multiplayer communities. It's also known that Knights are, as a unit, one of the most powerful units in the game that are used for arguably the best timing push (competing only with Tanks).
Giving a UU Knight with additional movement (basically what is already the Knight's, and every cav's, strongest feature) the potential to attack twice, coupled with Scythia's cultural heal-on-kill ability, is just laughable levels of overpowered. A UU Knight with additional movement would already be outright fantastic, but the fact it's with Scythia and can attack twice? That's a timing push that no other Civ in the game is going to be able to counter if played by equally skilled players.
It's bad enough she can already zerg you down with light cav in the first 30 turns if you're unlucky enough to spawn next to her, but now you have to worry about a second inevitable medieval timing push from 5 movement double attacking self healing knights? That's just honestly way too much. This UU as is would be far too good on any Civ, but is just absolutely over the top with Scythia.
but I made a couple changes to your mod for adaptation into mine and I wanted to talk about them here.
