The airlines need to get their act in order and enable something like this. With United having the CO call center basically whacked out for a while, the standard "use the phones" or go to a kiosk (and use the phones there) just doesn't work fast or well for most all either; and staffing at the larger airports is insufficient to handle even seasonally expected irregularities of this nature.

While I'd hope there would be something like this in the near future, I doubt any US airline will have something like this by this time next year .... mostly because any override authority given directly to travellers themselves will mean some game the system or possibly even mess up things more. Then there's the whole issue of amending instructions for checked baggage too.