BTW, I DO realize that X does not have any built-in facility for changing
resolutions on the fly, but if xvidtune can do it, so can nvidia, I think.
That's not correct. X can change resolutions on the fly via the randr extension. If you like a graphical tool you could use krandrtray (if you use kde; I'm sure there is something similar to this tool in gnome, etc) or use xrandr from console ('man xrandr' for help)
Anyway: Seeing support for TwinView an TV-out in nvidia-settings would be cool
For easy configuration you could also check yanc42: http://www.nvnews.net/vbulletin/showthread.php?t=55402