Here is the collection of mods I use to make the campaign harder. I am not a big fan of AI modding and besides I wouldn't really know what I am doing. Therefore, each of these mods makes simple changes to campaign mechanics that affect the player.
MORE WAR WEARINESS: https://drive.google.com/open?id=1DX...38-kSqA9NxPfOc
This mod increases the rate at which war fervour decreases per faction you are at war with. My hope is that you won't be able to keep war fervour in the positive through battles alone.
GREAT POWER PENALTY: https://drive.google.com/open?id=1GL...Actd7kunEspoYp
This mod increases the great power diplomacy penalty (that scales off a factions fame).
NO FOOD LOWER REPLENISHMENT: https://drive.google.com/open?id=1FG...2YnQHSilrm8-DY
This mod drastically increases the replenishment penalty for your armies in the event that food becomes negative.
FOOD UNCHANGED BY TAXES: https://drive.google.com/open?id=1cz...bLQC_cq02TJxsw
This mod stops tax level from affecting food production. Increasing taxes will no longer save your starving armies.
DYNAMIC SUPPLIES: https://drive.google.com/open?id=1cP...jAcg0iE5hETtEs
This mod doubles the rate at which supplies are gained and lost. This makes the supply system more dynamic, and you should run out of supplies more frequently
MORE MEANINGFUL ESTATES (MOD PAGE): http://www.twcenter.net/forums/showt...ingful-Estates
This mod makes handing over estates cost money (to represent losing control over that estate), conversely stripping estates will earn you money. My aim with this mod is to make estates more than just quick fixes to character loyalty.