Hi! Here's another chance to be reminded that Gentoo is about choice: how about a config file that comes with a pre-set list of packages that are important (if they're installed), for example e2fsprogs, the init system, stuff like that. But the user can add to this list (cryptsetup if it's needed for boot, the critical service this machine provides (say, apache), openssh because the machine is in a small metal box just off William's Field, AQ). Then, come update day, those packages, if to-be-emerged, are highlighted and/or there's a message at the bottom of emerge output (you /do/ a pretend run before you upgrade world, right?) warning that special care must be taken.
Just my €0.012 (adjusted for inflation) Regards, Tobias