If you find mass upgrading and pillaging+reconnecting too busted then mod the game to change that.
I don't find it busted at all. On the contrary, I would find it busted if such upgrading got removed. I'd even say that, if anything, the Mongols and India are busted, since you simply can't do horseman -> cavalry upgrades with either of them once you have horses and have upgraded all of your horseman from before you learned Chivalry. They had to make it so that horseman to cavalry or knights were possible for most civs, because a civilization can lose resources like iron or saltpeter easily, including human new player lead civilizations. The Mongols and India not having the same ability makes them much inferior choices militarily, and it isn't like the Mongols have builders advantages either.
But I guess if Flintlock was able to make the AI's worker management better in the future there'd be people complaining that it's "not what the devs intended".
I wasn't complaining that Flintlock did things outside of the devs intent. I did notice that, in my opinion, he did such. But, you Predator, like others (including myself previously, but not along) have called his mod a patch:
No one is claiming Flintlock's patch is for "balance" purposes.
If something is a patch, then it will be consistent with what the developers intent was. If something is not consistent with what the developers intent was, then that something is not a patch. And in my opinion, it differs from the developers intent. In some respects. So, to speak accurately, it's not Flintlock's patch. It's Flintlock's mod.