Personally, I would love to see different voice lines come in as a purchasable or blue essence available options. This idea has taken off in other games such as Overwatch. Almost all champions have set voice lines that range across all of their skins such as Varus, with the only difference being voice effect modifiers on each skin. Although this create a common theme across all skins of a champion it also does not provide any customization to those champions. Only having 1 to 2 different lines for each joke, taunts, laugh, or dance takes away from the uniqueness of skins. I think this would be a very interesting addition to League and would even possibly include interactions with skins that share themes like Dark Star or Super Galaxy.