That sounds great in theory..but in reality for most of us it's not a problem. I have three access points in mesh running 2.4 and 5Ghz SSIDs. I've switched as much as I can to zigbee at this point and have been rock solid. Most of what's left for me is zwave in wall switches. I use the IRIS outlets which are absolutely amazing repeaters for zigbee. So there goes your penetration problem. If there were more zigbee switches this would be even less of an issue. I also was an early adopter to the XBees, which allowed me to see very easily into my zigbee network and what was repeating to what. They also make excellent repeaters and for very little $$.
The Lutron switches were my substitution for lack of zigbee in wall switches. I have about 10 wall switches left that aren't a priority because they are working. Eventually those will be lutron also.
Xbee info:
