Glad you're thinking about currencies, but I think you're fundamentally misunderstanding what a store of value is. If you just "pick a number" that signifies what the medium represents, then anyone can just move in an out of that medium at an infinte supply. A perfectly stable store of value comes about as liquidity goes to infinity. This is impossible, but improves when one opens up a completely free market economy in both space AND time (ie exchanges and futures/options contracts)... and most importantly has a significant supply/demand that tries to determine the price of the actual "currency" or "store of value." The U.S. dollar is the dominant global currency because it has the highest liquidity (is accepted in a very high percentage of other countries and dealt with when transacting with Earth's most precious commodity... oil). If a number is just made out of thin air by the community, then there is no market created to price the store of value, and by definition, will never be used.