In this case, that is feasible. But there will be other incompatible systems that your base game will not anticipate - for example maybe there are two magic system mods, one for flat mana and one for body chakras (different magic levels for different body parts). Since Mechaenetia base doesn’t have magic events, the magic system mods add the events themselves. The flat mana mod does not include body parts in its API or events, as far as magic levels are concerned.
Another mod purports to apply negative effects based on low magic levels, but is written for the chakra magic system - the author didn’t know about the flat mana mod and has since discontinued updates.
Another mod adds a magic-eater monster, which siphons your magic when it attacks. But the logic for the attack is written for the flat mana mod, and a player with the chakra magic system won’t have their magic drained. This mod author didn’t anticipate other magic systems and didn’t leave any custom events for a compat mod to hook on to - because no (hitpoint) damage is dealt, no base Mechaenetia damage event is fired.
Now some player sees the above two mods and wants a magic-eater monster who will drain your magic, causing negative effects if your magic levels get too low. But the mods are incompatible - upon running the game, no matter how long the monster attacks, the player suffers no negative effects.
It is possible to write a compatibility mod that will calculate flat mana based off chakra levels, and intercept any flat mana system events. But even that approach isn’t perfect.
Consider one last mod that adds a “reflect” spell, written for the chakra magic system. The “reflect” spell is like a shield around the player that will take any magic attacks and reflect them back at the attacker.
Our player wants to be able to reflect the magic-eater monster’s mana siphoning attack, so that he ends up draining magic from the monster. Due to the way the monster and mana mods are written, draining magic from the player and increasing mana on the monster are two totally separate events. No information in one event links it to the other. So even with a compatibility mod, the reflect spell only reflects the magic draining portion of the attack: the monster drains its own magic and it increases its own magic by the same amount. Where the player expected to drain magic from the monster, but from his perspective, the “reflect” spell simply neutralizes the monster’s attack.
~Max