Seriously, I've already thought of a system:
Health – a separate stat that determines the amount of health.
Will – effectiveness of earth magic, number of AP (action points), strength. The latter is needed differently for different weapons: it has a greater impact on two-handed weapons, a lesser impact on bows, but it does have an impact.
Life – effectiveness of fire magic, number of MP (movement points), damage resistance
Reaction – effectiveness of air magic, evasion, initiative
Concentration – effectiveness of water magic, accuracy (melee and ranged combat), resistance to negative effects (reduction of AP, MP, various paralysis and other debuffs)
Here are some comments: evasion is primarily about reducing the minimum damage that an opponent can inflict with an attack. Completely ignoring damage is only possible if the minimum damage is zero, which is possible for opponents with low accuracy or if you have high evasion. Additional points in evasion thus increase the probability of this "critical miss." Advantage: characters with normal evasion and accuracy will not ignore damage every other hit.
I haven't decided about damage resistance yet... It would be good to give resistance to an absolute amount of damage for a greater difference from evasion (which reduces the minimum damage by percentage). But most likely, it will also be in percentages, otherwise it will be difficult to balance. Absolute damage will definitely be reduced by armor (it's especially difficult to break through bronze plate armor with a stone dagger).
By the way, I decided to abandon mana for simplicity. There will just be action points.