Excellent work Kongdej. I will be adding these units to my next game to see how the AI does with them! I am testing my weapons balance mod, but all the same traits and weapons exist in my modded version of CoreWeapons.xml and anything that will encourage the AI to utilize units that have sensible trait combinations will help me test my changes. Thanks!
For myself, every game I design a mounted scout with scouting, underdog and finesse using a spear. This unit typically gets a +6 to attack, and can often survive minor scrapes with small wandering monster packs on the far sides of maps. In my mind, it is critical to get a high movement scout unit out as early as possible, before map movement becomes diplomatically impossible. I usually send one in every major direction (so typically 3 total) as soon as I can get horses.
Besides fast moving scouts, there are two other types of units I favor:
1) cheap, low resource (metal, crystal) units for fodder for monster lair cleaning and/or hero assistance early in the game. i.e. spears, finesse, bloodthirsty, enmity (if being used for cross kingdom/empire war), or spears, finesse, underdog, bloodthirsty (if being used for lair cleaning). These units aren't intended to last forever, but rather to get your champions through that awkward stage where they can't kill 3 mites by themselves.
2) elite, resource be damned, maximum armor + shield + 1 handed weapon (or 2h maul sometimes) with maximum equipment (+attack and + init), mounts, cloaks, and traits. If I'm researched up to plate mail, then you're forced into strength and muscle traits to go along with bloodthirsty. If it's earlier in the game then you are able to take all +damage traits. This unit will be tanking, and living for a long time, so I want to make it worth it's wages.
One of the reasons I found myself modding the CoreAbilities.xml and CoreWeapons.xml was that some choices in the vanilla game are so clearly better than others. Bloodthirsty at the endgame provides +7 attack to a unit wielding a maul, as opposed to other traits like Fury or Spell Resistance which are so clearly inferior. Now when Spell Resistance provides +40 spell resist... all of the sudden there's some tension in choices. 