So who do we eliminate? Rooks, Knights or Bishops?
You will have players leave because of their loyalty to a Chess piece, and don't think for 1 minute it would not happen.
It will not change anything. 
Plus, the maps would have to be rearranged, some coding would need to change,.....based on a gamble?
Any time there are big changes you risk a big exodus. Look what just the radar caused.
Not to mention what if most players chose one side over the other? A MA in constant 75 to 25.
This has been a losing debate for 35+ yrs.