we tried this and Dries was not amenable at the time. Maybe a few more opinions and modifications would help. See http://drupal.org/node/79008
Yeah, that's a major nuissance. Can't we add a "no cache" bit to the variables table? Variables marked such, would not get added to the cached version (and bloat it) but would be retrieved from the table each time when needed. This would be perfectly acceptable for e.g. the password reminder mail templates.
I imagine it would be ok to set the value of this bit based on the length of the stored string. We already do something similar for the locale cache where we do not store strings longer than 75 chars in the cached version.
The result of this would be:
1) better performance for most pages (the ones that don't require one of the long strings)
2) somewhat worse performance for a few pages.
3) no guilt trips for abusing the variable_get/set functions once more. :p