You can't make mining 15% easier. You can only remove one difficulty bit making mining 50% easier. This means you will have a newly proposed block in ~5 minutes and then exponential big number of proposed blocks after 10 minutes based on the number of mining pools.

How do you distribute the rewards then? You could go with 50% of the block reward goes to the original difficulty block proposer 25% goes to the -1 bit difficulty proposers, 12.5% to the -2 difficulty proposers and then limit this number to whichever number of recepients we are willing to store in the block.