Aight, so I had this idea quite a while ago and I've thought it through and it seems like it would work. The idea is simple... When old leaves or pitchers die, you cut them off and let them decompose on top of the medium. There is one major flaw to this, which is that it would grow mold, however I really don't think this would happen in a greenhouse with high light, temperature fluctuation and great air flow. If you're an outside grower, you've probably noticed springtails in your medium... Or at least I have. I find spring tails, all different types, living in my sphagnum cultures. These guys would be great decomposers. You know how mushrooms pop up every now and then? Those would be good too. Over time, say over the period of a year, the leaf would completely decompose and turn into compost that Nepenthes could actually use.
What are y'all's thoughts on this? Of course, I would put the dead leaves under the live sphag on top of the pot so it doesn't just go to the sphagnum. This HAS to happen in the wild, and it will happen with neighboring plants too, so it should be safe for Neps.