Basically, my initial idea was simple : a couple units on either side, rigidly paired up by relative positions, every turn you choose an action out of four available for each unit (attack, block, dodge, special), and then it is simultaneously carried out. Whichever unit has higher speed stat will go first in each respective pair. Simple.

But then i thought, too simple. It doesnt really take any advantage of simultaneous command execution. Might as well be a traditional turn-based game. No. So i increased the number of available actions-per-turn to 3. So you could set a unit to attack-attack-dodge, or dodge-attack-defend, or any other of 4-in-power-of-3 sets. So you could plan a bit in advance, and be more careful, or you'll get hit three times in a row. In addition, the enemy units will always telegraph their first, and only first, action. Much better, i thought.

But it wasnt enough. Then i thought, what if any two actions could combine and create a new action ? For example, attack-attack becomes strong attack. Defend-attack becomes a counterattack. Dodge-dodge becomes escape from battle. And so on. I liked this idea alot, but it brought way, way too many troubles. For example, do i force the player so that EVERY two actions become combined, or let him choose if he wanted to combine them or not ? And since i have 3 actions per turn, do i combine first two or the last two ? And will i be even able to invent 16 sufficiently unique actions ?

But i couldnt let it go. So, i thought, let's lower the actions-per-turn to 2, let player choose if he wants to combine them or not, but limit the number of combined actions in one game to a reasonable number like 5, and make a quest like system to have player gradually get a choice of a new combined action out of total 16 available through a quest system of sorts. Might work, i thought, and made this post.

So...did that make sense to anyone and what are your thoughts ?

Sounds interesting, is movement involved at all? Or are we talking more of a Final Fantasy esque type combat, where units don't move?

First, I would say that having things such that "Attack + Attack" results in a single "Strong Attack" or "Defend + Attack" results in a "Counter Attack" has a potential for confusion on the player's behalf that you don't really need to add to a turn based game. It'd be different if it were a button mashing tournament fighter sort of thing where response time and number of inputs is limited. But I don't see any reason not to simply provide the player with selections for "Strong Attack" and "Counter Attack" where those selections take up two of the three slots for action that you're providing. Make it clear to the player what their options are.

But as for the new direction you're asking about taking your game, limiting the number of special actions available within a game could work depending on the game itself. Providing a way to replenish those actions or discover new ones could also work, again depending on how you fit it into your game. I can imagine a strategic war game where each player starts out with 3 missiles that can execute devastating attacks. Having the game such that new missiles (or whatever) are hard to come by, it's up to the player to use them wisely. Could potentially be quite fun.

What exactly do you mean by a "quest system" though? It sounds RPG-ish. Are you thinking like multiple levels, each with a mission, where upon completion maybe a new unit is revealed?

is movement involved at all?

There is no movement in combat. Final Fantasy is as good analogy as any, i suppose.

I don't see any reason not to simply provide the player with selections for "Strong Attack" and "Counter Attack"

Well, there is truth in that, i agree. On the other hand, overwhelming the player with choice is something that also happens. Imagine this : you want to attack, you select a unit and click the "attack" icon, it falls in the first of three empty slots, and two more icons appear to the side, one is another "attack" - another is "strong attack". Would that not make you think : "i already decided to attack, but do i want this guy to perform something a bit more specific than just that ?" ?

You might also think of it as not an entire separate choice, but instead as a "follow-up" if you will. IF you "attack" - you can "follow-up" with a "strong attack". Does that make more sense ?

What exactly do you mean by a "quest system" though?

Just a generic system, perform specific task to gain something optional. Say, stun and capture enemy leader to learn from him the "parry" command, or something to that effect.

I see what you mean.

I dont accept your postulate about what multiple slots should correspond to (for example, how does the recent XCOM two-action system fit in your theory ?), but i do agree about the disastrous possibilities of a muddy ruleset. I guess what i'm saying is, i dont understand how what you described is any different from every other game with discrete action system. Are you not making arbitrary guesses anyway ? If you picked up some game today, you wouldnt be able to guess and\or exploit the enemy's actions, therefore some guesswork is involved no matter what, is that not so ?

But anyway, if it comes down to being able to predict the enemy's actions with at least partial certainty, like i said, you will always be able to know the enemy's first action in a row, so it's already neither arbitrary nor random.

There are other ways to make it less so, enemies can have patterns, they may react in specific ways to your specific actions, there can be a special command or even a special unit the whole role of which is to reveal every action of a single enemy.