I like the idea of rating decay but am a little concerned for pawns who may play a number of types of games but overall not many games of each type ... I think the decay period probably needs to be longer and possibly logrithmic, say 100BKR if nothing in 90 days, and additional 200BKR if nothing in next 90 days, 400 for next 90. There would also have to be a consideration of the minimum rating. Another idea would be for the decay to be percentages of BKR ... 90 days 5%, 180 days 10%, 270 15% ...

I think the details still need to be worked through but I like it!