The purpose of the Beertokens trust is an attempt to create a more stable currency that will not change in value more than between +-3% over time so that merchants can start using crypto currencies for what they were meant to be used for instead of just speculating.
If I have understood correctly, you wont accomplish what you are promising, because its basically imposible. The price of anything, including a currency is determined by supply and demand. You are controlling the supply and it wont change more than your 3%. But the demand is unknown and can be very variable, so you basically can not control the price.