We should support 'new ActiveXObject("MSXML2.DOMDocument");' We could simply map this to impl.createDocument(). It might fix a number of compatibility bugs, who knows.
I have long since forgotten what site had this that was bugging me.
Looks like we don't have a long list of sites that would benefit from this, and thus no incentive to "start any further down the activex slippery slope", per Eric's own words.