It would be cool to rebalance a few champions into hybrids.

This isn't necessarily a balancing issue, it would just be a good way to differentiate champions that are way too similar or have no niche. It gives them their own build with new options so they're not just inferior on-hit or auto attacking AD champions. There are really only a handful of true hybrids in the game, Jax, Akali, Kog'maw, and now Shaco and Katarina. Every other "hybrid" is pretty much just an AD or AP champion that has one or two passable hybrid ratios and wants a hybrid item.

Corki is by far the best candidate to become a hybrid. Before you tell me "Corki is already a hybrid" well... it's complicated. He does hybrid damage but builds full AD. His damage is roughly 70-75% magic damage but his AP ratios are pitifully outclassed by his AD ratios. This gives him very inefficient options for penetration or lifesteal/spell vamp. He wastes 80 AP on Gunblade if he wants the omnivamp. Giving him full hybrid ratios would make him unlike any other ADC.

Aatrox has innate issues due to his rebirth, so that always needs to be considered, but even then I think he could be greatly improved if he were made into a hybrid. He's outclassed by other on-hit champions like Warwick, Yi, Shyvana, Irelia, even Kayle. Making him a hybrid would turn him into a completely unique champion. He'd be most similar to Jax, but still very different, because Jax's biggest weakness is lack of sustain while it's Aatrox's biggest strength.

Warwick is being reworked, but he's just another good example for my 'add hybrids' argument. He has 1 good AP ratio that doesn't justify him building AP, and tons of on-hit magic damage that can't be changed by AP. It makes another weird champion that has very contradictory final builds just like Corki. He'd be another cool champion to give some options to with additional AP ratios.

Obviously balancing changes would need to take place on most champions that had this treatment. I think it would be great to carve out a niche for a few champions with an identity crisis, and maybe even use it as a way for balancing toxic champions. The next time a champion is "impossible to balance" it'd be worth a shot seeing if they would be better as a champion and better for themself as a hybrid.