I think you may be looking at this backwards - MMC is just a means to
perform tasks, so the correct answer is to make sure that only users/admins
who ought to be able to perform those tasks, can do so. What specifically
are you trying to protect?
Yes give the administrator "Author mode" for his/ her snap-ins. You'll have to use user mode(if that's what its called) for limited accounts. The lower mode has the options you were looking for.
Is there any way I can secure [password protect] the MMC
to prevent users from changing system settings?