Personally I think this is a really interesting idea and find some appeal to it. My only concern with this is that while destroying blocks that some may seem to be annoying and useless it will also destroy resources like gold, iron, diamond, and such. This would be a side effect of exploding blocks that I believe many players would dislike. However, to give my personal opinion I like the idea and would be interested in hearing what others have to say about it. I think it would make mining very interesting and harder for those that find it too easy. It would also give it a kick for those that want more excitement out of the game. With a creeper being able to explode blocks there would be the possibility of the ceiling exploding and lava falling on your head if you mine at a level lower than 11. If you mine at 11 you could lose your ground and fall into lava. Really with this change the possibilities are endless.