If (the amount of unconfined transactions > some limit && the last 2016 blocks contain 9x% of 1MB worth of data)
decrease the difficulty by x %
This means:
Faster transactions if needed
More transactions if needed
More inflation if needed
The block reward driving mining costs will be obsolete sooner and the 21 mil coin limit can remain *only it will happen sooner
This method provides an economic incentive for large miners to spam the blockchain with many very small transactions, which is one reason why it will never work well.