People dont really care for the mechanic.
Just use regular combat with 3d movement and recycle the weapons for the clases in regular combat.
You get a riffle variation and a single and 2 handed spears (spears and tridents respectively).
Conditions need to be normalized:
1- SINGLE PLAYER conditions stack on DURATION.
2- MULTIPLE PLAYERS conditions stack on INTENSITY.
3- REBALANCE condition duration, damage and application.