"AREAS" Current number of areas, use "0" if area-less.
"ROOMS" Current number of unique rooms, use "0" if roomless.
"CLASSES" Number of player classes, use "0" if classless.
"LEVELS" Number of player levels, use "0" if level-less.
"RACES" Number of player races, use "0" if raceless.
If people are interested in a community effort to create a list of 'unofficial' variables I'd be happy to link to the outcome.
Maybe Kavir is interested in organizing the effort, his past suggestions have been pretty useful to me, and he appears to be mentally stable, unlike most of us.