The idea is to release purchasable models, voiceovers, and effect changes that are compatible with all current and future skins. Essentially allowing you to pick the model, voice, and effects to have a kind of "build your own skin" system out of the parts Riot decided to release. Ideally, these would be compatible with all skins including the default so that if you want to make a small change to the default, you can, or if you really like a certain model and want to change its effects, you can. This idea originated from the disappointment I frequently saw in friends when they saw a new skin with a really nice model that was stuck with default effects and doomed to be a cheap skin, both figuratively and literally. This would, in theory, make every skin that has ever been released ever desirable, because maybe people liked an old skin but wanted better particles, or a voiceover for it, and this makes that a possibility.