Here's an interesting thought that I had: why not make it possible to have a second passive skill slot? Maybe by way of a coupon that you buy with ZC that adds the second slot, like adding stash. This would make it possible to have, say, counter AND charge at the same time. One of the other pros is that it would encourage more people to buy ZC, thus supporting the game. I bet a lot of people would jump at the chance to have a second slot
Now, it's very likely that this second slot could make the player OP, so here are some limitations I was thinking of:
1. Second passive is only useable in Sector mode. That way PvP and BvB stay fair (or at least, as fair as they already are xD)
2. Level II skills can't be used in te second slot. To go even further, maybe Level II shouldn't be allowed in EITHER slot (while using two passives). That way, you can only use Level II if you're only using one passive.
3. No skill stacking. This means you can't stack counter or leech, and thus double the effect or power of those skills...
Let me know what you guys think of this, and also if you can think of any more nerfs that would help make a second slot less OP.