This sounds very good to me. We can all agree that HF20 didn't go as well as it could have, so I'm all for any measure that might prevent this problem from happening during the next hardfork.
One thing I was thinking about though, that I haven't seen anyone talk about, is the potential for witnesses to add bounties to people who can break the testnet. From what I understood, the testnet didn't really have a lot of data, but a bounty might attract a lot more people to test it. I'm sure the top 30 witnesses would not have too much trouble pooling in for a bounty. This last part is obviously directed towards all witnesses on the blockchain, not only @reggaemuffin, but it was something that popped into my mind when I read the post and comments here.
On the radio show @jedigeiss and @techslut suggested that Utopian could post a bounty for users to break things. Which is a great idea so my witness pledge factors it in and asks for an environment where such a bounty can actually have an effect.
Ah, it's great to hear that other people also had this idea. Let's hope something like that could happen then. I can definitely see some people trying their best to break the testnet if they could get a few hundred STEEM or so for doing it.