As I am an avid chessplayer, did you do know that Chess evolved quite a bit over time?
Of course it had many origins, which varied in pieces and size of the board, etc. but even if you only focus on the "classic" chess we know today and neglect variants like Chinese Chess, etc., it didn't start out right away.
Examples:
Pawns could only move 1 field forward in the beginning.
The bishop could only move 2 fields.
The queen was the weakest piece, hence pawns couldnt be turned into something else when reaching the enemy line, which makes for a total different strategy!
http://en.wikipedia.org/wiki/Rules_of_chess#HistoryMost changes were then introduced to make the game faster and more exciting.
So M.U.L.E. DOES suffer from being slow paced from a modern perspective (i believe the pieces went so slow in auctions because of limitations of the machines back then handling 4 player simultanously), while still being a good balance from what was technically possible.
PM2 is an attempt to tinker with how certain parts could evolve, while preserving the original idea, just like chess evolved, by adding bonusses to species to make them stronger or more varied, etc.