I'd say push it back further, like the 15. Currently kicking short and forcing a return tends to end in your favor and the opposing team usually fail to reach the 25 yard line. I don't know if the possibility of getting them to start at the 20 is enough to risk them starting at the 25 when teams tend to stop returns before the 25. Also, quite frankly, I don't think kick offs get enough love, nor do defenses get enough help. Having the defense get super pumped and congrats a kicker as they take the field on the 15 would be great.
And despite the NFL thinking that moving from the 20 to the 25 would reduce returns- it hasn't. Teams still go for it. Making it more rewarding to split the uprights would have a drastic reduction in returns, which is what the NFL really wants.