Assuming there aren't any significant changes to the protocol to allow more on-chain transactions
Why not make a block every minute? Make the reward 1.25 bitcoin so you still average 12.5 bitcoin every 10 minutes. You still get 12.5 bitcoin every 10 minutes but you get 10 times the number of transactions confirmed.
Why stop at a minute, make a new block every 10 seconds, every second, again with a proportional reward to maintain the average of 12.5 bitcoin every 10 minutes? could get a *lot* more transactions processed and more quickly.