Head on over to F.O. for my latest Varsity Numbers if you haven't yet seen it. In it, I look at the percentages behind Greg Schiano's proposal to abolish kickoffs.
If we were looking to replace an onside kick with something similarly successful, we would actually need to look more in the fourth-and-12 or fourth-and-13 range. Fourth-and-15 might feel like it's easier to convert than an onside kick is to recover, Rod, but it is not. It is quite a bit more difficult. And if Charlie Weis, or any other coach, wanted constantly to try to play make-it-take-it with the rule change, power to them. They would probably be looking for another job soon, but they can try.
(And on a side note, I'm pretty sure this makes close to 7,000 published words for me today. If that's not a record ... well, I'm not sure I want to know what the record is then. I feel simultaneously pathetic and heroic.)