FWIW, my wish would not only be for jQuery to "do the right thing" when I call $.getJSON(), I'd also like it to figure out if we're in a CSP environment. (Currently, I do 'typeof 'chrome' != 'undefined' && chrome.tabs != null' - as an example, which detects if my code is running in a CSP-restricted Google Chromium extension background page - but CSP's restriction on inline-scripts can - and will - appear elsewhere.)
jQuery is known for sniffing internally what features are and aren't available and to compensate for them/choose the one; the presence or absence of CSP restrictions could be viewed similarly.
The part I really don't like about my proposal is that it would require manipulating the URL to remove a 'callback=?' clause, which would entail some assumptions about the structure JSON-P URLs.
Perhaps this is better located in a plug-in.