Ummm… The best way is buff the normal UT or adjust it instead of destroying the game design of the tech tree structure. The later one may cause the serious problem what is out of the range of “civ balance update”.
For example, the Nomads of Mongols can cost 450W200G rather than current 300W150G, changing the effect into reach the population max cap like Huns.
For other normal (or useless) UT:
Royal Heirs: Cost 150F150G instead of current 300F300G.
Madrasah: Cost 400F200G instead of current 200F100G. Also make the relic generate gold faster by 100%.
Orthodoxy: Also make the own units resist conversion more by 33%, and the own units that have been converted lose 40 HP. (Since the Slavs has no Heresy.)
Cuman Mercenaries: Cost 650F500G instead of current 650F400G. Change the effect into that the allies’ and the player’s oldest existing TC would pop out 15 Elite Kipchaks immediately once this tech is hit. These Elite Kipchaks would occupy no population. (The allies should not worry about building a castle and the population.)
Atheism: Cost 300F300G instead of current 500F500G. Also make the own units get great attack bonus vs. Monk, Missionary, Monastery and Wonder.
Inquisition: Cost 300F300G instead of current 100F300G. Also make Monk and Missionary train faster by 33%.
Lmao, this is hilariously OP