Below is how I like TC will work in EWOM.  I want it to be simple to understand, but provide a lot of variety for both humanoid and monster units. 

How I would like Tactical Combat (TC) to work

-    All TC should be finished in 12 turns, keep it somewhat short
-    Keep the total number of stats minimal; I suggest only ATT, DEF, HP, DAM, SPEED, MOVE, Weapon Reach,  Cover%, (and maybe Luck%, Morale)
-    Allow dozens of effects that modify the stats mentioned above, e.g. exhausted, poisoned, paralyzed, etc
-    Allow only 1 type of physical damage; Blunt/Cutting weapons damage vs different armor type is very boring & complicated to represent
-    Allow a handful of mental, magical damage/resistance types
-    Discourage Kiting in TC and strategic map

The Battlefield
Zone of Control (ZOC):   Your enemy cannot bypass your surrounding 1 tile ZOC unless their SPEED is way higher than yours; e.g. the Mongols.  ZOC is bypassed if your unit’s Total HP is way less compared to your opponent; e.g. a lone ranger cannot hope to hinder an elephant charging towards him.

Flanking mechanism: most normal humanoid units are vulnerable at its back

Turning mechanism: if there are more than 100 units in that tile, normal humanoid units need 1 turn to turn their facing 180 degree

Back stepping mechanism: if gamer need to maintain their facing direction & there are more than 100 humanoid units in that tile, normal humanoid units can backstep only 1 tile per combat turn

 Troop formation mechanism

- Each TC tile can only hold a maximum predefined number of troops, depending on the Size of the individual troop.   For example, a tile can only hold 2 Gigantic sized Dragon, or 500 Medium sized humanoid Infantry, or 200 Large sized Cavalry.
- When your stack has 2000 infantry units, the game automatically split it into 4 at the TC deployment stage.   This provides variety because each occupied tile has its own ZOC, representing additional choke point that your opponent cannot easily bypass

- A hero/Sovereign who learnt “Deployment skill” will have some flexibility to adjust this maximum, so there can be more Total HP in a tile, or use a more spread-out formation (thus gaining more ZOC)

Battle Tactics:  Some specific units/hero can push/pull their opponent on the TC map during an assault.  If the Total HP of the pushing/pulling unit is higher, they have better chance of succeeding.   For example, if your dragon can pull your enemy one tile closer, so they become within your archer’s attack range. 

How a unit is designed will make a huge difference in Tactical Combat
   
First Strike:    determine which party gets to strike first by adding SPEED, Weapon Reach and Height Difference together.  For example:

A fast Calvary (SPEED =5) carrying a sword (Weapon Reach =2) will be able hit infantry (SPEED=2) carrying a spear (Weapon Reach=4) first; only those surviving infantry will then response with a retaliation strike.

However, if the same infantry is standing on higher ground, enjoying a Height Advantage of 3, the infantry will instead get the first strike, because 2+4+3 > 5+2

-    And it does not mean Spear is always better than Sword, because sword is allowed to strike twice in a combat turn, potentially dealing more maximum damage.  
-    Weapons like Spear, lance etc will reduce flying/mounted opponent SPEED by 50% in the first strike calculation
-    Flying units usually strike first, because they have natural Height Advantage

Cover %:  Each unit has a Cover % that will be added to the tile terrain’s inherent Cover %.  This % is compared against projectiles attacks like arrow, canon or breath weapon (half effectiveness)

- For example, a dense jungle has a natural 100% cover, when someone hides there, those units become invincible against projectiles.    Another application of Cover%; breath weapon check against Cover%, but it will naturally cut the effective % to half.

- Units equipped with shield increases both Cover% and DEF.  However, the larger/heavier the shield it is, the more it reduces the units’ SPEED and/or MOVE.

- Units hiding in terrain with high Cover% will become ‘invisible’, unless 1) some opponent unit is right next to it, 2) some opponent is on higher ground & close to it, or 3) it made a ranged attacked last combat turn & remained stationary this turn.

SPEED (vs Evasion): 

-   Units have a 10% chance of completely evading a hand-to-hand normal attack, for each 2 points SPEED advantage you have over your attacking opponent
-   Each spell has its own SPEED (modifiable by caster level).  Your unit can evade a spell if it has a high enough SPEED.
-   Different ranged attack has its own SPEED.  For example, if there is gun as a weapon, it is a really high SPEED ranged attack.
-   SPEED is mostly based on the unit’s fraction (or the inherent SPEED if it is a monster), and how it is equipped.  
-   And during TC, your unit’s SPEED stat is also adjusted by many factors, for example:
A} Unit SPEED is reduced in certain proportion to the % Total HP lost during combat since turn 1.   It means if your unit has been severely damaged after a few turns, it cannot evade, become more vulnerable to first strike, or spells etc.
B}  High Morale, or good commander leadership
C} Units located in a swamp/river terrain will have SPEED reduced
D} Units with Exhausted, Paralyzed status will have greatly reduced SPEED

E } Spear/Lance units will have its SPEED reduced if they are in forest/jungle

Any comment or further suggestion?