Maplestory should have a "Pro" server

And even hacker/botters have a limited supply of accounts with level 150 chars.

That is a good point, although even today a few regions of Maple are still overrun with hackers and/ or botters.

I would not say that the boss is fool proof but with the power limitations of the level range, etc, it will be pretty easy to detect if something fishy is going on and to have a GM instantly descend upon them to deliver righteous justice. (the one exception being if the character is way over leveled, which would explain unusually high damage)

I am not so sure that hacking can be completely prevented. Depending on how the server would do then if they are needed, there might be a chance to dream up some extra countermeasures.