Say the difficulty of the bitcoin network was not variable. Then regardless of the network hash-rate, the mining puzzle will be the same. What would that mean in terms of the security and economics of the bitcoin network?
If everything else remains equal, then I'm assuming that mining a block becomes easier and easier and we will have mined all 21 million bitcoins much sooner. Besides this, will anything change security wise? And if so, can anything be done to maintain the decentralised consensus and fiscal policy of the network with a constant difficulty? For example, the block reward payed to the miner becomes inversely proportional to the number of parent blocks.