I would find a command line option for portage interesting to merge only stable packages ignoring the settings in ACCEPT_KEYWORDS or package.keywords. I'm runnig a unstable system, with some packages unmasked, some nightlies, but while testing it's sometimes interesting to install a stable version of a package. Currently there's the possibility of searching for the latest stable and specify the version directly, or to use ACCEPT_KEYWORDS="-* amd64" emerge -1 $PACKAGE with amd64 corrected to the architecture of the system. For me something like emerge -1 --stable $PACKAGE would be a nice feature, maybe --unstable or even --masked for the opposite direction. All not intendet to be used for normal merges, but only for oneshots. Maybe it's just my laziness, but maybe there are other people who agree on that.
Maybe the option should be called --stable-keywords, to clarify that it doesn't change anything other than ACCEPT_KEYWORDS. There are existing related --accept-properties and --accept-restrict options. For consistency we could also add a similar --accept-keywords option, but that would not be much different from how you currently override ACCEPT_KEYWORDS.
