Great ideas @reggaemuffin which is why I know that @ned and Steemit Inc will completely ignore everything you have said in this post because they have made it clear they like their rogue fluid approach to development and releases.
From what I know Steemit Inc. would really appreciate the witnesses to give such a pledge. But that is for them to state. If all witnesses are saying that they will not adopt a fork with X then Steemit Inc. knows what is up and won't do X, as we saw with HF17.
From the things you mention. Many of these are already there or not possible in the way you said them. Depending on Steemit Inc. to cure us all is in my opinion not the way to go. And yes, we need to hold witnesses responsible. And to be honest that is the task of all witness voters. Like in politics, if you dislike something, talk about it.
But I digress, this post was about the witnesses owning up to their part of the responsibility and publicly stating their stance on how development goes. If a witness will take your list as requirements, then definitely vote for it :)
I have to admit I agree more with @beggars than with you when it comes to the responsibilities of the witnesses. AFAIK few of them are experienced developers or sysadmins while many Steemit users have such a background. Requiring witnesses to run a test node seems absolutely reasonable to me but it's a major change in how witnesses are chosen and that's why I'm afraid it ain't gonna happen. Because for 35 years we all expect computers to work, not to be maintained heavily.
What should not be forgotten is that all of this could be a blue-print for other blockchain-based projects but I suppose you're already aware of that ...