Kassadin needs a rework, but Poppy-scaled

I would rather put the title "How to make Kassadin good without being flat OP" I'm a relatively new player from LoL, but I have played other MOBAs such as DotA and Smite. I have played Kassadin ever since I started with League, and I have seen his history as a must-ban-or-useless champion. Investigating about his origins I have seen that he's inspired by DotA hero Anti-Mage, and as him, he was meant to be a melee AD carry who does well against mages. It seems that, as he had incredible base damages and ap scalings on release, people built him AP and RIOT thought having a -1 sec cooldown flash on a one-shot assassin was cool. IMO that's not even close to being healthy, and that's what brought him to being a below-average outclassed assassin. Why not bring back his original identity as a melee carry with unmatched mobility? This way, he could be good without being outclassed by literally every other assassin other than resisting mages' poke a bit better. Right now the two only worst assassins than Kassadin are Nocturne and Evelynn, who have to build friggin' tanky to be effective. If I have time and this thread gets some responses I will edit and post some ideas about the anti-mage carry that Kassadin should be.

TLDR: Kassadin should be an auto reliant melee carry to be potent and healthy at the same time.

I've got some ideas: Innate: Void Stone Passive: Kassadin receives 15% reduced magic damage, and converts that mitigated damage into attack speed.

Q - Null Sphere Active: Kassadin fires an orb of void energy at the target enemy, dealing 70/95/120/145/170 (+50% AP) and silencing the enemy by 1/1,25/1,5/1,75/2 seconds. Also, it marks the enemy, and the next basic attack or Riftwalk against that enemy increases Kassadin's attack speed by 20%. Range: 650 Speed: 1400 Cost: 80/85/90/95/100 mana Cooldown: 12 seconds

W - Nether Blade Passive: Kassadin deals 10% AD bonus magic damage, that also increases with critical hits, and restores mana equal to 200% of the bonus damage dealt. The mana restoration only procs against champions with mana. Active: Kassadin's basic attacks gain range, mixed penetration equal to 10/20/30/40/50, deal bonus magic damage equal to 2/3/4/5/6% of the target's maximum health and restore mana equal to double of the passive amount. Range: 200 Cost: None Cooldown: 6 seconds (at the end of the buff) Duration: 4/5/6/7/8

E - Force Pulse Passive: Kassadin draws energy from spell casts in his vicinity, gaining a charge whenever him or a nearby champion casts a spell, capping at 5. At 5 charges, Kassadin can cast Force Pulse. Active: Kassadin emits a pulse of void energy, dealing 80/130/180/230/280 (+60% AP) to all enemies in a cone and slowing them by 40/50/60/70/80% for 1s. Range: 700 / 80° Cost: 80 mana + charges Cooldown: 6 seconds

Ultimate (R) - Riftwalk Passive: Kassadin has 5/10/15% omnivamp. Active: Kassadin blinks to the target location, dealing 80/100/120 (+20% AP)(+2% maximum mana) magic damage to nearby enemies upon arrival. Each subsequent Riftwalk within 15s increases its cost by 50% and increases its damage by 40/50/60 (+10% AP)(+1% maximum mana). Range: 700 Cost: 100 (+50% per stack) Coodown: 8/6/4

With a kit like this, I see him building Botrk, Maw of Malmortius, Essence Reaver, IE, and even Guinsoo's Rageblade.