I like publically available rules. So here is my suggestion for the Perko Videogame Rating System, or PerVid (:D). PerVid is a derivation of the ESRB system, with rules that are universally applicable and open to public scrutiny. Plus, it also knows what "play" involves.
The ratings are:
Early Childhood (any game rated "E" may be rated "EC", as the publisher sees fit)
Everyone, 10+, Teen, Mature, AO (My AO is 21+).
The things which affect the ratings are as follows. You take the highest rating any of your content demands. Please note that I have replaced the alchohol/drugs/tabacco combination with "destructive addiction", which is really the important part.
References to alchohol or tabacco: 10+.
References to an addiction of any kind which is destructive or degrading in any way, or references to drugs which are publically considered to cause such: Teen.
Rewarding or requiring play utilizing said substances: Mature.
Blood and Gore
Situations where there is a perceived chance for injury or death: 10+.
Depictions of any kind of permanent death: 10+.
Depictions of sentient or developed characters permanently dying: Teen.
Rewarding any kind of permanent death in gameplay: Teen.
Rewarding any kind of permanent death of sentient or developed characters in gameplay: Mature.
Violence is not an independent concern. Violence is covered under "blood", "danger", "death", and "degredation".
Language, Mild Profanity
Language, Extreme Profanity
Clear sexual references. For example: dirty jokes, sexually suggestive clothing, nonrealistic "nudity" (such as statuary - any nudity containing no genitalia or female nipples). Teen.
Nudity, sex. Mature.
Depictions of sex utilizing illegal or denegrating techniques. AO.
Player can bet real money on games of chance. Mature.
Here are the ones I added:
Mod Friendly: Graphical Substitution
Player may make or acquire new graphics for game, so game may contain, though no fault of the publisher, nudity and suggestive attire. Teen.
Mod Friendly: Level Substitution
Player may make or acquire new levels for the game, so game may contain, through no fault of the publisher, explicit language. Teen.
Mod Friendly: Gameplay Substitution
Player may make or aquire entirely new gameplay for the game AND game may contain human-like characters. Mature. (AO?)
Game contains highly moderated on-line play: 10+.
Game contains on-line play in which players may communicate unmoderated: Teen.
Depictions of highly unrealistic mild degredation, such as dropping anvils on cartoon characters, non-harmful slapstick, or non-degrading insults: E.
Rewarding use of cartoony degredation in gameplay: 10+.
Depictions of "realistic" mild degradation, such as physical harm, psychological harm, threat of same, begging, etc: 10+.
Rewarding the use of mild degradation in gameplay, in any way: Teen.
References to extreme degredation, such as torture: Teen.
Depictions of extreme degredation: Mature.
Rewarding the use of extreme degredation: AO.