1) I think humans and orcs can use gate, but maybe requiring more/less wizards per cast... Maybe elves get to recall back 5 units per wizards, Humans/Orcs the standard 3 units per wizard.
2) Gate should break protection... castle passing, and then defending with full army from retals seems disingenuous. The person attacking cannot even find pretal if the castle already passed.
3) Elves can train wizards at at faster rate 4:1 (standard school 5:1 wizard)
4) Buff up Caragous...
5) Buff up Wolf Masters...
5) Knights require 1 sword, 1 plate, 1 horse, 1 Spear (as per unit description with "lance")
6) Dwarf gold production bonus
7) Orc GH houses 50 units (between standard and gnomes)
8) Unpopular Opinion: Gate can be casted offensively without giving retal like TS (eg. Ally Elf recalling units from an enemy back home to be slaughtered in a following attack/retal/pretal).
9) Unpopular Opinion: Knight Charging reduce additional damage taken to 10%
10) Unpopular Opinion: Elven Elite Archers add light armor (defense can increase with tech), but nerf basic attack to 4 (instead of 5).
11) Mages upkeep to 20:5 (instead of 30:2)
12) Better rates for Iron to Gold and Wood to food (maybe elves get rate bonus).
Not sure how hard the coding will be, but just some thoughts