So please forgive me if this is a rather naive question. I haven't seriously used Windows in nearly 15 years.
I seem to recall runas being a lot like su, in that you enter the target user's credentials, rather than your own as in sudo. This works because sudo is a setuid executable, and reads from configuration to find out what you're allowed to do as the switched user.
Is the behavior of windows sudo like unix su or unix sudo with regard to the credentials you enter? Can you limit the user to only certain commands?