I don't know if my take on difficulty is that valuable since I didn't find tactician that easy. But these are the levers I'm thinking of pulling for a more difficult playthrough.
1. Never load anything but the most recent save except in case of a bug, never load if the game can be continued. 1a. Quicksave whenever a fight starts 1b. Quicksave whenever a fight ends 1c. Quicksave at the end of every conversation 1d. No saving in conversations
2. Never move or pick up explosive barrels. 2a. No crate stacking.
3. No pickpocketing merchants.
4. Ban or fix the following 4a. Tavern Brawler 4b. Haste 4c. Lore Bard's Cutting Words 4d. Pact of the Blade's extra attack 4e. Multiclass wizard spell scroll learning 4f. Phalar Aluve 4g. Staff of Spell Sparking 4h. Stat fixing items. (Headband of intellect et al)
5. Don't sleep until a party member complains about being tired 6. Use a mod to add a 25% xp debuff
I might have missed some exploits, the game might be still way too easy for some. But it seems a reasonable base to me.
