The most telling thing that jQuery (or any other library) could do would be to have a policy that any browser bug workaround has to be accompanied by both a) a bug report to the browser vendor and b) a corresponding test to the relevant W3C testsuite. That would put public pressure on browser vendors to fix the issue, and provide the jQuery team with a convenient way of telling when the workaround was no longer needed.
Speaking as someone that has spent time working on a web browser, that would be a fantastic policy, both for browser developers and for web standards in general.
Sadly, from what I can tell, at least some browser vendors (and more importantly the developers working for them) don't particularly care about whether they pass W3C test suites....
