mrpolo, rather than mess around with the weights of the factors in the RPI, I would rather see something that uses SOS as a multiplicative factor to adjust the AWP (adjusted winning percentage). For example consider this hypothetical rating system:
HRS = SOS * (2 * AWP + SOS - .5)
I chose the factors here so that if SOS = .500 then HRS is the same as AWP. If your SOS is above .500, then HRS is greater than AWP; if SOS is below .500 then HRS is less than AWP.
Someone would have to crunch all the numbers to see if this formula really works -- I'm not going to since there is no chance that it gets adopted.
Actually after a little thought I see that the formula is flawed at the low end; when the AWP and SOS combined are less than .25 it starts increasing for lower SOS. Doesn't matter for comparing good teams though.