I want Chrome and Firefox to show badly formed XML in full plaintext format instead of telling me that it's badly formed and showing the first few characters of the offending plaintext.
This could potentially be useful for any web developer when dumping variables and such.
I can't speak for Firefox, but this is simply the way that XML is handled in Chrome; the parser is draconian, and error messages in parsing are raised to the user via the UI that you're unhappy with. :)
A quick search of the bug database doesn't show any similar requests to point you to, so I'd suggest filing a bug with your feature suggestion via http://new.crbug.com/ I can't promise that anyone will implement it quickly (especially given view-source as a viable workaround), but at least the suggestion will be tracked in the system for others to find and vote for via stars.