Perhaps my wording was unclear. I propose that the minimum PoW difficulty to submit all transactions stay the same. So the process of sending IOTA or sending a message in a zero balance transaction would stay the same and still be available for all IoT devices around the world to do. If miners (Different from regular users) wanted rewards through inflation however, they would have to compete with their fellow miners, and come up with a transaction of a high enough difficulty that it would limit all reward able miner transactions to only being rewarded every increment of a set time-length. Similar to how the difficulty in bitcoin changes so that blocks are made around every 10 minutes.
Edit: Moved a sentence to a more relevant place.