I agree with what's the the "XML" section.
I'd also like it better to represent all slots in the same way; I have added an alternative proposal to Multi-Content_Revisions/Dumps now.
For compatibility with existing consumers of dumps: I expect that most of these consumers just grab the data from the first <text> tag. That will continue to work exactly as before. With the new proposal, there will now just be more text tags, which will probably be ignored be legacy code. And more attributes on the text tag, which will also be ignored by old code.
Removing the <model> tag from the revision is a breaking change. Perhaps we can just keep the main slot's model there for a while, but include a comment that this is deprecated.