An 8 song EP for Christmas. They did it with Lies, do it again! Checkmate, General, Soulmonster, Thyme, etc.
Take a few months off to vacation. Then meet back in the studio and write and record an album as a band.
I feel there are many industry factors you aren't taking into consideration. Everybody doesn't win in that situation. For hardcore GNR fans eager for new material, yes we win if the band releases an EP of previously unreleased studio recordings for Christmas this year. However, the band doesn't necessarily win in that scenario. The label doesn't necessarily win in that scenario.
The anticipation and media & retail cooperation for the next full length would be greatly compromised by the release of an EP. The best strategy for a legacy artist in GNR's position would be to make sure that the next new song the public hears is the lead single for the next full length album. It would also be in the best interest of a legacy artist in GNR's position to allow plenty of time between releases to maximize the chances of the media treating the arrival of a new release as extremely newsworthy.
You are a fan. You want to hear new music from one of your favorite bands. Very understandable. However, when you say that "everybody wins" if an EP is rushed to market, you are ignoring the potential harm to the commercial viability of the next proper album.