Single Comment

There is a way to do what you want.
 
Create a set of dummy positions for each player which will be the amount
of pieces which have this particular attribute.
 
Place on each of these positions dummy pieces.  Let's call them
'Token'.
 
When a piece has its attribute specifically changed, capture one of that
player's Tokens.
 
Have the loss-condition set to 'pieces-remaining 0 Tokens'.
 
If you need to toggle this condition, instead of capturing the Token,
change it to a piece called 'null'.