They already react slower, have more limited senses, and don't move around as good on lower skills. They also don't use all of their skills or class abilities on lower skills.
The bot_nightmare cvar was an attempt to sorta do what your talking about, except in reverse: you could have idiots who had great aim.
I could add an aim variable to the bot's .bot files. I'll think about it, check the code, and see from there.
