A champion that adapts

So with the reveal of Kayn, we kind of got a champion who can adapt to the needs of your team, either as an assassin or a bruiser.

I was thinking of a champion that adapts to the enemy team, based on the damage type that they do

Passive: Gains bonus armour or magic resistance based on the damage type done by the enemy. He starts with an innately high armour or mr, but he transfers points from armour to mr and vice versa depending on the type of champion he is fighting. But he does not gain armour or mr per level. His armour/mr will never go below a certain amount. This is so that he doesn't get deleted when ganked by an opponent of a different damage type. If he is fighting 2 enemies of the different types or a hybrid damage champion, he will gain increased mr and amour but at a much lower rate. I would put in that he will gain increased health when the majority of the damage to him is true, but there is no champion who deals mostly true damage.

Q: Gains bonus attack speed and armour penetration when fighting against enemies melee enemies, and gains bonus AD and reduced attack speed when fighting against ranged champions. I used melee and ranged because most ranged champions are squishy and need to be bursted down while melee champions are tanks and need to be worn down. in an ideal world, he would gain the bonus AD when fighting against squishes while bonus attack speed and armour pen when fighting against tanks people. This is a point and click ability, so that he cannot get both when a tank suddenly shows up when he fighting an adc/mage. Q applies grievous wounds on the enemy champion.

W: Significantly increased resistance against the most recent form of crowd control on him for 5 seconds. For this crowd control is divided between slows and roots/stuns. When he is being slowed, he will gain massive resistance to slows (unto 75%) but increased stun/root duration, and if he recently had been stunned, he gets massively increased resistance (unto 90%) to stuns but increased duration on slows. When activating this ability he gains increasing movement speed towards enemy champions.

E: He gains the passive ability of the most recent champion killed. Now this is a pretty wild idea, since some passives will be utterly broken (Ashe's, Braum's) while others will be utterly useless (Illaoi, Tahm Kench). The way to balance this is that he only gets the one of the most recent champion he killed, so if he wants to keep the passive he has to kill the same champion over and over again, which is not a good idea.

R: Ultimate evolution, this skill basically lets him fight in team fights. He gains all the effects of his Q and W (reduced effectiveness) and does % max heath true damage on his auto attacks.

He has to do a bruiser style build, with 1-2 damage items and then tank items. Since he has no scaling armour/mr, he needs to build tank items to allow him to switch points from armour to mr and vice versa. He doesn't have any cc, but can chase well unless they enemy has both stuns and slows in their kit. He can do extremely well against team comps which do not have mixed damage threats, as high armour/mr scaling can go incredibly high (almost taking 95% reduced damage, but this value can only be achieved when in combat against the same damage type for more than 10 seconds).

As with evolution, sudden change is his weakness. While his resistance to one damage type can go incredibly high, his weakness to the other can go incredibly high (to the point of almost taking true damage). He also does pretty bad in team fights without his ultimate, as team fights usually have multiple damage types and champions.