Okay, play around with this:
http://fbe.am/uJAIt's developmental, prototypey, but I *think* it works like it should.
bot.qc has the various skill accuracies as constants, you'll see them under the extra shizz here block.
Lots of crap at the bottom of bot_misc.qc.
You can change the various personal accuracies of weapons as well as favorite weapon in the botname function. Note that positive values will cause them to be less accurate, while negative values will give them more accuracy, compensating for skill level accuracy. Note final accuracy (in bot_angle_set) doesn't go any lower than 0, because once they hit that level, they don't get any more accurate. I've also added some accuracy stuffs for the grenade launcher.
If this works out okay for you I'll tell you how to integrate it into your own sourcebase.