This might be possible if you're not unlucky with the guys you get.
Forget about all the talk about flying starts. With such a wide variation in talent and ability level, you want the slow guys to run the shortest and the fast guys to run the longest distance.
There is a 20 meter relay exchange zone that can be used to your advantage. Have the fast guys grab the baton right at the beginning of the exchange zone, even if this has to be done from a pace that isn't much faster than a slow jog. They shouldn't give the baton to the slow guys until they reach the end of the exchange zone.
This will take some practice, but having multiple attempts will take the pressure off. If we're not limited to standard track rules, that 1:40.9 becomes a lot easier. The fastest guy runs 300, the next fastest runs 250, and the slowest and second slowest guys run 100 and 150 meters, respectively. The splits will be something like 38, 31.5, 17.5, and 13.9.