Security :: Sudo Non-user/non-root Password?

Stumped on this one. I'm trying to set up limited sudo authority on a desktop with some sensitive user data, and as an extra precaution I wanted to configure sudo to use a password other than the user's or the root's. I'm not sure how to do this. From the manual, we have a few options, such as "runaspw" or "targetpw", but none seem quite what I'm looking for.For instance, "runaspw" could be used if I created a user for nothing other than sudo(ing) purposes, but it requires you set "runas_default", which means that said user would have to have authority to execute said commands in the first place. This is workable, but seems like a lot of extra configuration for each specific command that I want to run, as well as creating some issues with simply commands such as "shutdown" or "reboot". Also, "targetpw" can be used in conjunction with a sudo(ing)-only user if I set an alias, but, again, this isn't quite what I am looking for.

Ultimately, what I am really concerned about in this situation are keystroke loggers, so I would prefer to avoid repeated entering the user or root password when performing administrative tasks. Also, I would prefer not having to create a sudo(ing)-only user as mentioned above to prevent a comprimised password resulting in an attacker being able to log into my system.