It would be really nice to have some way of editing the META tags. Yes, they may be abused at times by spammers. And no: they aren't dead, or completely ignored by search engines.
One particular area where they would be useful, are the Google Webmaster Tools. The functionality seems very similar to the one for Google Analytics - you get a key, and the system makes a simple tag out of it. So for starters, it could be adapted from that '3rd party tool'. (Also note that there are many people screaming for it over at wikidot forums.)
I would be happy if the Webmaster Tools were available. But the general capability to edit Meta tags would be very useful by itself.