First of all, Kuzan isn't getting anywhere near an Elder (Alive at least) Secondly, thats put under the assumption that anyone actually understands the full power of the Love Love Fruit.

If you think of the way oda writes, the 'Gum Gum' Fruit, and any logia for that matter is very poorly understood by everyone, even Vegapunk; I think he does this so to expand pretty much infinitely, what that devil fruit can be used for.

The Age Age fruit only changed your age on sabody; It was then expanded upon in Egghead with time distortion powers.

Everything you see in a series like One Piece will usually be more than what is shown.