First of all, as someone already pointed out, our terms state that your VIP can't be taken away from your account. As with the discussion on taking away fast skins, we can't just retroactively change the terms and conditions for something you have already paid for. The terms just state the (obvious) fact that if you lose access to your account, you also lose access to the VIP tied to it. Because of this, we won't be adding this as a punishment.
We've had this for a time in the old PTP, and there it already proved to be not a good way of punishing, until Tenshi even forbade a couple of years ago. It was too inconsistent, some people got banned for something and lost their VIP, others got banned for the same thing and didn't lose their VIP. I think the reason he forbade it was because he got in trouble with PayPal because of it. So there's also that to keep in mind.
But, my main point against this form of punishment (in my opinion), is that VIPs should be treated the same as a normal player. This works in one way (VIPs not getting a preferential treatment), but I think it should also work in the other way (for example, VIPs not getting a worse punishment than a normal player). I don't see any reason a person should grt a different treatment, better or worse, just because he paid for a VIP account. Some VIPs are very regular players and have played here longer than anyone else, but some VIPs are new players and buy VIP within a week of playing. There are also regulars that have been playing here longer than anyone else, but aren't VIP, either by choice or by constraints. If they break the rules, we can't take anything away, so should they get a better treatment and a different punishment just because they aren't VIP? You could say that, because they've already bought VIP, they probably have enough money to buy it again. And yes, for some people that might be true, but for others it might be a big purchase and they might not have the means to buy it again. So, all in all, I think there should be an equal treatment for all players, and being VIP or not shouldn't influence that.