Miscellany

import bpy

USER_KEYCONFIG = 2
wm = bpy.context.window_manager

# border selection
for k in wm.keyconfigs[USER_KEYCONFIG].keymaps.find('Gesture Border').keymap_items:
  if k.propvalue=='SELECT' and k.type=='LEFTMOUSE' and k.value=='RELEASE':
    k.any=False
  if k.propvalue=='BEGIN' and k.type=='MIDDLEMOUSE' and k.value=='PRESS':
    k.type='LEFTMOUSE'
    k.shift=True
  if k.propvalue=='DESELECT' and k.type=='MIDDLEMOUSE' and k.value=='RELEASE':
    k.type='LEFTMOUSE'
    k.shift=True
  if k.propvalue=='SELECT' and k.type=='RIGHTMOUSE' and k.value=='RELEASE':
    k.active=False
    k.alt=True

# circle selection
for k in wm.keyconfigs[USER_KEYCONFIG].keymaps.find('View3D Gesture Circle').keymap_items:
  if k.propvalue=='DESELECT' and k.type=='MIDDLEMOUSE':
    k.type='LEFTMOUSE' 
    k.shift=True
  elif k.propvalue=='NOP' and k.type=='MIDDLEMOUSE':
    k.type='LEFTMOUSE'
    k.shift=True