For deciding who goes first each action phase, I have decided to give each unit an actual Initiative score. The total of these scores, from all unhindered surviving units, from among the army creates a total for each player. The highest total wins; players can break ties by forfeiting actions to add +d6 to this total for tie breaking purposes. If only one player forfeits at least one action, they automatically win.

I'm starting to think that not only will measuring contact ranges be rather tedious and slow, but ultimately, in a skirmish level game, rather pointless. Unit coherency rules only seem to be used in games really as a logistical process; a way of keeping the table tidy.

I'm think that maybe each Commander (army leader) generates a Contact range. No other unit within the army. Instead of measuring ranges and dealing with enforced consequences, any player without a single friendly in his commander's zone of influence, forfeits an action at the start of each turn (when players generate their pool of actions for the turn).

In a two person conflict with equal number of starting "points", there seems to be no reason to not use ALL of your actions up front, since you're basically just trading back and forth regardless.
e.g. Player A and B have 10 actions, player A wins init and uses 4 actions... he will then have to wait while Player B takes 4 unopposed actions before he can go again, so they're both getting 4 actions in a row unopposed.

This kind of mechanic might work better if you bid a number of actions and then combined that bid with a die roll (I'd suggest something "curvy" like 2d6, so a large number won't necessarily ensure a win). The highest roll then gets to act, ties going to highest bid AP then highest natural roll. You could have the number difference between the two rolls influence how many turns the character gets to act before another bid and roll is required. I'd suggest 1/2 the difference in rounds (rounding down). You could also allow for someone to sit out a roll, basically allowing their opponent to win, and thus recover some actions. I'd make it blind bidding, so you take a die and set it to the number of AP bid and cover it... when everyone's ready, you show at the same time.

E.g. Player A and B both have 10 Action Points (AP). Round 1 they both put a 10 sided die down with their AP bid. When they're both ready, they call out to show. Player A bid 3 AP while Player B bid 6 AP. They both roll Initiative (2d6) add their Leadership and their AP bid (we'll assume a leadership of 0 for both). Player A rolls a 5 while Player B rolls a 7. Player A thus has an 8 result while Player B wins with a 13.
Player B has the initiative and can take 2 Actions (13 - 8 = 5 / 2 = 2) before a new roll is forced. On the next roll Player B only has 4 AP left while Player A has 7 AP. This time Player B bids 4 while Player A bids only 3 again. Their rolls come up as 8 for A and 6 for B. Player A just barely wins (11 versus 10) and gets one action (11-10 = 1 / 2 = 1).
The next roll, Player B has no AP while Player A has 4. Player B bids 0 and A bids 2 AP. Player B will recover some AP (d6?), since he did not bid. Luckily he rolls a 12 while Player A rolls a 10. This results in a tie, but since Player A bid more AP, he gets an action (but only one) before they must roll again.

Just a suggestion on how to make these things more dynamic...

That's easily solved by having the number of actions dependent on the number of units. Even if the game happens to start with the same number of units per side as players take casualties they will find their pool of actions becoming more unique.

I also had the idea of giving each unit an Initiative score. This way the person who started first each turn was decided by the total of his remaining units' Initiative. His pool of actions is then a separate entity.

Actually, before we go to far to that...

Is this a heavy simulation, moderate simulation, or a light simulation?  Are you writing up a microgame or squad leader. I think you should define the amount of detail and simulation you want, before we continue on.

moderate to light.

That is, the rules should be simple to understand but providing tactical depth. Like chess, perhaps

A flattering comparison obviously, but that is essentially the aim. What I don't want is a disparate series of rules and contexts further subdivided by a plethora of further rules and contexts (do X, except when B is happening, then do Y, but not after A happens...)

Simple, in my mind, doesn't mean simplistic any more than light means without detail.

The players should be able to grasp the basics very quickly, leaving them free to devise strategies, create units, etc.

I'd appreciate someone taking a look at the rules i've written thus far. Maybe there are some important concepts that i should include. I can PM the word files.

What's the advantage of resolving more than one action at once?

Here is a new idea that I think works better:

The Action phases:

There are two action phases to the turn. At the start of each, players pick one of their remaining action tokens to determine what the majority of their units will be doing. Action tokens previously used are spent for the turn.
There are three types of action a player can choose with a related stat and a single token to denote its use.

Movement, which is superior to Attack. Related stat = Speed.
Attack, which is superior to Guard. Related stat = Attack.
Guard, which is superior to Movement. Related stat = Command.

Where an action is superior to another the player has Tactical Superiority (or just Superiority).

Where a player has movement superiority, each of his units is considered to be +1" further from all attackers, for the purposes of range.
Where a player has attack superiority, they roll 1d10 and pick the best number on their attack rolls.
Where a player has guard superiority, they may interrupt any moving enemy that is in range to make an immediate attack as their attack this turn.

Initiative:

To determine who can act during each phase, one player makes a Tactical Roll, using d10. Each player may activate any units whose relevant stat (Attack, Movement or Command) is no greater than the result. The player who then has the most active units may give them actions first, followed by the opponent. If there is a tie, resolve randomly.

Each player then totals the Initiative scores of all inactive units; they then activate all such units. The player with the highest total acts first, followed by the opponent. If there is a tie then the player who last acted starts.
During the second half of the phase the inactive units do not enjoy tactical superiority bonuses. They also can engage in any single action; however guard only lasts until the end of each phase.