Effect of weapons upgrades

Best thing I've found to do to prevent mass exploitation of this +6 upgrade is to make the cost of upgrading weapons in the EDU much, much more expensive. Like literally 5 times the default value. I'm loathe to remove the functionality completely since I enjoy the graphical changes to the weapons on the battlemap.

In terms of the Easterns factons one just has to even up the score a little. For example, enabling Dismounted Boyar Sons and Druchima to contribute towards Swordsmiths for Russia, Dismounted Sipahi and Naffatun (they actually have swords) for Turks, as well as Naffatun and sopmething else for the Egyptians. I actually enabled Sudanese Tribesman to be built by the Egyptians and Moors so that should help them. Also, one can allow HBGs to be built in castles and that lessens the spread of Swordsmiths Guilds considerably.

Well increasing the cost of the upgrade wouldn't do much for newly trained units who come out with upgrades already though. Only for units you send in for retraining.

I know, but retraining units effectively is easily one of the main things that differentiates the human from the AI; moving units from one city to the next to get the latest upgrades. That at least puts the dampners on that.

Swordsmith's Guild also does not have to be limited to dismounted infantry. Cavalry have swords too, mighty fine ones at that. e.g: Mamlukes, Ghulams, Sipahi.