Is nokton acceptable by itself?
Instead of saying the full bonan nokton, is it acceptable to simply say nokton?
There's a famous saying attributed to I believe Don Harlow: "You have the right to say whatever you want and I have the right not to understand you."
Slightly more serious answer: Sure, go ahead. I expect if it were to catch on as a slang expression, it would be shortened even more to "Nokt'!" (See "Sal'!")
Extremely serious answer: Learn Esperanto first and use it before you try to start messing with it. You may find it doesn't need any messing at all.