Yes, of course it's possible, but the developer has other things to do, Nightbot is a side-project worked on during free time.
It doesn't make much sense to disable commands once they're added, that's why it's not an option, I gave you a work-around, if you're not happy with that I don't know what to tell you.
Of course, users will still see the command, but if they look at the userlevel, they'll see that they can't use it, they can even sort the list by userlevel so they know at a quick glance which one they can use, but that won't prevent people from trying to trigger the "disabled" commands, even if you really could disable a command, users would still remember that the command exists and would try to trigger it, so the results are the same.