Champ Idea: passive/aggressive support

hi everyone, i´ve been thinking of this idea for a while. Reading Syndra´s lore i came out with the story of a mage-monk apprentice, who is the very opposite to Syndra. Instead of unleashed power he prefers controlled power. And its from his discipline with Syndra´s master, that he learned to control his own power and others, controlling damage received and using it against his enemies, while protecting his allies. His name is Diaman, and he is looking for avenge his master´s death, trying to control Syndra. This are the abilities that i think for him (but i can´t explain percentages of damage or cooldowns because im not familiar with it, or how it function) :

Passive: Disciplined Power: Diaman don´t use mana or energy. His life bar is divided in two Instances (kind of Kled) .Depending on which instance he is in, his abilities change. With full health he is in Defensive instance, where he gives best ally´s buffs and his abilities cause less damage, but slow enemies. Also his autoattacks cause less damage. Half or lower health, he enters in Aggressive instance, where his abilities are more offensive, and deal more damage and CC. His autoattacks cause more damage. If he recovers health he enters in Defensive instance again.

Q: Force Hit:

defensive instance: Diaman hits the air causing a force wave. The wave travels slowly, and increase its radium at max range. Enemies hitted by the wave are slowed. If they are near Diaman at the moment of the hit, the slow effect its bigger.

aggressive instance: the force wave travels faster, cause damage, and knock up enemies. Enemies near Diaman, are stunned.

W: Mental Blocking:

defensive instance: Diaman creates a mental barrier that absorbs damage and blocks projectiles (kind of Yasuo or Braum). Diaman can move while this abilities is castted. if its reactivated, Diaman can leave the barrier in the place he is standing, and the ability goes on mayor cooldown.

aggressive instance: Diaman absorbs a percentage of all damage dealt in a small area around him and after a moment he delivers a percentage of that damage absorbed, as magic damage.

E: Centered Impact:

defensive instance: Diaman hits de middle of a big area, and creates a force wave that travels slow. Allies hitted by the wave get a shield, and a small speed buff. Enemies hitted are slowed.

aggressive instance: Diaman hits the middle of a big area, and creates a force wave that travels faster. Allies hitted receive a speed buff and enemies are knocked back. If they hit terrain they are stunned.

R: Fight Balance: While levitating, Diaman creates a mental shield around him that absorbs a percentage of damage received, and last for a few seconds. After then, the shield explodes and delivers force waves all around, causing a percentage of the damage absorbed. The waves hit with terrain and rebound in the opposite way.

Well, this is the idea, a champ kind of tanky, focused on block the damage going to the vanguad, to then back off and regenerate health to change instance and be able to protect his allies. This will make some windows of combat in his gameplay. With the idea of balance the fights, using enemies damage as his own damage think he won´t need much dmg items. I thought him as a melee champion, but that can change. I don´t know if his kit fits entirely in his thematic, for example his ultimate which i was thinking could be a Totem, or somethng like that, that creates a war zone where allies are benefited of fighting in.

So give me your thoughts. Sorry for not being accurate in some information.

hope you like it.