Perfectly balanced combat conditional skill charge mechanics are perfectly balanced
Creating new custom skill components for "This Skill gains 1 Charge if Combat Condition is true on Combat", "This Skill loses 1 Charge if Combat Condition is true on Combat", and "This Skill loses all Charges if Combat Condition is true on Combat" was WORTH IT! I've also added custom components that work the same way but with Skill Stacks. And a custom component for losing all Charges/Stacks at endstep if condition checked at endstep is true.
A Berserker could use this for an "Enraged Berserker Rage of the Berserk Raging Berserker" Skill where he deals an extra 2 DAMAGE for every attack he makes with an Axe at 1 range, up to a maximum of +12, losing all stacks if he goes a turn without attacking with an Axe or attacks with anything other than a 1-range axe or gets healed. He can also have a "Lose all Stacks if combat condition is true" component checking if he's being targeted on his turn by an ally with a healing spell!
Personal Skills can gain Charges and Triggers based on what happens to them, who's doing what to them, and what they're doing, during your turn or the enemy's turn or both!
A Sage could build up charges to increase their damage every time they rotate spells between Fire, Water, and Nature in the proper cycle.
Mounted Archers could get bonuses for darting in and out of combat and lose their bonuses when attacked.
A Ninja could use this for a Skill where he deals +10 Damage on every attack after the 2nd one made with Throwing Knives but loses all charges for his buff if he gets hit. And another skill where he has a 100% chance to dodge the first attack made against him by an enemy during enemy phase if in Cover. A Covert unit could also gain an attack bonus if he starts his turn in the correct terrain or initiates combat on the correct terrain. A Ninja unit could also get a Ninja Teleport skill that's like Warp except it warps you to enemies or uses a ninja KUNAI WITH CHAIN to pull enemies to you. Perhaps the first attack a Ninja makes with Poisoned Knives during that Ninja's turn will deny counterattacks, ensuring the Ninja doesn't need top-tier defensive stats and the ability to dodge tank reliably to survive applying poison debuffs. Maybe Ninjas could have Ninja-only AOE items that debuff foes and deny counterattacks. Maybe the Ninja could get a buff for every enemy they attack at under 20/30/50% HP and execute in a single attack. There's a lot Ninjas could get to provide party utility and debuffs and enemy disruption while fulfilling the class fantasy of being a thieving poison-loving evasive stealthy damage dealer without becoming a broken overpowered cheater like Fates's Sol Ninjas.
This could be used for many things and it will take a while to balance. Because this system calls the skill charges skill charges, I might have to rename the charge mechanic (That thing where some skills start granting a bonus if you didn't attack last turn, and that bonus is lost after your first attack) to something completely different. Wouldn't want players to say "I am fully charged!" and then get confused whether this means the unit has Charge or the unit's skills have Charge. Perhaps... "Focus"? Yeah, Focused could work. "Prepared" or "Clear-Minded" or "Rested" or "Energized" or "Empowered" could work too. I'll work on it.