Ok i understand. Well that would be interesting of course but why should you do it? It’s to linear.
Lets take it seriously. Example:
Race with 100 riders
90 riders have an AVG of 5 w/kg
5 riders have an AVG of 4.5 w/kg
5 riders have an AVG of 4 w/kg
So the TOP 25 will all race with equal base (5 w/kg)
So the TOP 26-50 will all race with equal base (5 w/kg)
So the TOP 51-75 will all race with equal base (5 w/kg)
So the TOP 76-100 will all race with different base (4, 4.5 and 5 w/kg)
Well you could try it but it won’t be super amusing because it is in no way different from the way it is currently. Just people would manually join.
More intrestingly would by a point system. Basend on your racing experience or how many races you did TOP 10 or finished on podium and so on.
If you finish 3 races TOP 3 you will rise from E to D or
if you finish 10 races TOP 10 you will rise from E to D.
I would keep it the way it is! With some aspects Zwiftpower.com is using. Meaning extend the table In-Game by some lines for a deeper insight in other riders performance output.
BUT the most important aspect is WHICH Powermeter unit is online!
Is it a SMARTTRAINER or just simple ROLLERs without resistance.
I guess there is still a lot of variability when it comes to POWERMETER units. Some show 30 W more or less than others. That is a huge difference!
You could double check Powermeters with Smarttrainers for example. I guess there is to much cheating involved. People buying certain Smarttrainers or PM which shows higher Wattage than others.
If you want a serious ranking think about that before! But here it comes to negative feedback for certain manufacturers and i guess this will be interesting if not impossible because some would definitely outclass themself by their buggy implementation of P = W / t what strain gauge and how many in use (these can manipulate measuring results over time!) and so on … Now you could you could create a race series which complety restrict their PM units to manufactor X or only Powermeter units from manufactor X, Y and Z are allowed but others not or even better you start a special society. Everyone on Zwift or Zwiftpower or both who is in the TOP 100 list will get a Powermeter unit from Manufactor Z and henceforth must use this unit in every race!
Peace and ride on! 
