Sniped by
@Crowsfoot .....well, here's my post anyway.
Why? That makes it harder for almost any army that isn't Seraphon.
It is bad enough as it is already, with the melee immunity and so on.
There are no such rules. In fact if you take them as written there is only that the wizard on top cannot move, and can dismiss it if they wish.
So there is no reason to assume the Vortex vanishes if the wizard dies.
But it clearly says it doesn't block movement if there is no wizard on top.
About balance of the whole thing:
Just two examples:
1. Right now you can win a game like "two places of power" against Ironjawz by teleporting a lone wizard to a mission objective, put it onto a BWV and defend the other objective with your whole army. There is no way the Ironjawz can kill that guy except with a lucky Maw-Krusha (its ranged attack sucks) or a REALLY lucky shaman. Same against some other armies. Basically every list that doesn't have a good amount of shooting and/or magic. Like a Sunclaw Starhost for example, or a Firelance.
2. A battleplan requires the enemy to kill your general (Assassination). Chances are good your general is a Slann, or even worse: Kroak. Put him on a BWV. No melee army can kill him in any way. The only chance would be magic but it is hard to do enough wounds to Kroak.
Bottom line: the rules should be completely rewritten IMO. It is a unbalanced POC right now.