I wonder what would happen if you were to let them dry out and then pulverize them to powder? Would they actually dissolve?
Anyway, I have a Geobin that I'm using exclusively for leaf composting this year for my raised beds. I suck them up and bag them with a lawnmower, which shreds them pretty nicely (though I've considered using a mulching blade to further reduce the size - maybe next year), and dump them in the bin. It would go faster If I turned the pile from time to time, but I'm lazy. As it is, I check with a pitchfork every once in a while, and the further down I dig, the more "dirt" I see. It won't do too much for the next several months unless I mix it up and add air and water (the inside of the pile will never freeze solid in this zone). It should make some really nice compost for the spring.
I have it next to another bin where I dump grass clippings, woodchips, garden waste, and kitchen scraps. Come spring, I'll compare.
Anyway, I wonder what the difference would be if you composted them before adding to the substrate. Possibly too much nutrients would be released too quickly? I assume they'd have a much higher nutrient content than a standard potting mix.