Sorry, but I don't agree with this.
To change just 1 individual stat like this completely takes the uniqueness out of a map. When a mapper creates a map, the stats work together to create a unique experience. To change one of them takes away whatever makes that map special. You might argue mods like Hardrock and Doubletime do this, but they don't change the map at all. HR and DT don't change, but rather they amplify what the map has to offer. They still preserve what makes the map unique / difficult while remaining fun for the players. Not only would this completely ruin the way mapping is done, it would only encourage more generic plays. How exciting would it be to see every map with cs4 and ar9? Nothing exciting to see anymore, is there?
Every map would in a sense become a pp map, because the player will just take away whatever makes that map special or hard to make it easier for themselves. The point of maps with unique stats is to create these styles, to remove that purpose only makes osu more generic.