I think combined items should be detachable into 2 component items so that we can use them to combine into better items when you get other component items. For example, you're having a Titanic Hydra, a Large Rod, and a Giant's Belt. If you could detach Titanic Hydra into Giant's Belt and Recurve Bow, then combine the Bow with the Rod and the 2 Belts into Guinsoo and Warmog respectively, that would be better than when you combine the Rod and the Belt into Morellonomicon, except when you're playing Sorcerer comp and need to have grievous wounds effect. Or when you have a Spatula and a Yuumi, but Yuumi is useless because the comp you're playing isn't Sorcerer and doesn't deal much spell damage, detaching the Yuumi into Spatula and Large Rod then combine the 2 Spatulas into a Force of Nature to increase team size by 1, that would be better, right?
And unequip items from champions, too. Your Jinx has a Bow and you need another Bow to combine into RFC, but in the carousel, only Vi has Bow. After picking Vi you have to sell Vi to get the Bow. But you haven't got any Hextech champions after refreshing the store many times, selling Vi only gives you zero chances to activate the Hextech trait. If you could unequip the Bow from Vi and then equip it to Jinx (to combine into RFC), Jinx would have RFC and the Hextech trait would be active, too, rather than when Jinx has RFC but the Hextech trait isn't active.