Earlier I mentioned I wanted the idea of punishing players who spam attacks. In fighting games, this is achieved by having a long recovery time from attack animation, back to idle animation. While in this transition, the player cannot do anything and is vulnerable.
Dark Souls also incorporates this idea into their combat. Likewise, just spamming the attack button in that game will leave you vulnerable.
What I will do, is this:
Any action a unit performs consumes stamina. Stamina naturally refills over time. In the point of view of this turn-based system, stamina refills a little at the beginning of the player’s turn. If a unit runs out of stamina, he undergoes a negative status effect, some sort of “Tired” status; a sort of debuff that makes the unit vulnerable. Until the unit recovers a substantial portion of his stamina, he will stay in that debuff status.
Any action done consumes stamina: even normal attacks, even moving. Only the “stand idle” action will not consume stamina.
This means moving is risky and should only be done when needed.
Either way, this stamina mechanic is simply very similar to action points, in games like XCOM.