Nasus rework suggestion, how to make him what he's supposed to be

Hello everyone, as a Nasus main since season 2, I would like to share my opinion about Nasus current state and my ideas about a possible rework. Right now, Nasus is in a meh spot. He is playable, he is quite decent, your laning is actually not as challenging as one might think, but your teamfighting is incredibly terrible and the item changes (fh nerf, black cleaver buff/ juggernaughts and freaking fiora with retarded %health true damage scaling with AD - whatever). But as a concept, he fails his identity. What I mean is Nasus is supposed to be THE lategame champion, which has a tremendously hard laning and is rewarded for surviving it, Nasus should not be let stacking and once he's really farmed up he should carry. Right now, it isn't the case.

1. Nasus laning isn't super hard. It might be hard some times, but not much more than other champions, really. And you have really good sustain
2. Nasus lategame is garbage in teamfighting. He gets pathetically kited and melted and can pretty much only fight the frontline (being kited), which means his potential damage is compared with carries damage, so it's kinda negligible (it is different in duels and in splitpush scenarios, because if he faces a carry, the carry doesn't have a comparable tankiness)

So I would like to focus on this : Make Nasus a high-risk, high-reward lategame champion. I came up with an idea, that sadly looks a bit like Cassiopeia system of stacks, and might look a bit overloading but pretty much satisfied my goals

1) Hard laning Base Health 561 --> 535 Health/lvl 90->92

AND

Stack system : +3/+6 +2/+4 until he reaches 200 stacks Then +3/+6 until he reaches 500 stacks Then +5/+10 until infinite^^

NB : reaching the +5/+10 requires the equivalent of 600 stacks in live, with a harder earlygame. You should not let Nasus reach this state, and even there the scaling won't be that crazy compared to what it was before. The early game should now be much harder, the fact you scale less fast until 200 stacks also reduces completely your overall power because it reduces indirectly your sustain, on top of the potions nerf it will be really a hard lane.

2) New : Powershifts

At 200 stacks, Nasus E grants him increased resistances when he fights in its zone. The increased resistances are solution 1) equal to the armorshred (20/25/30/35/40) solution 2) equal to 10% of the bonus damage of Q (example : 400 stacks -> +40 armor and mr)

I believe that with the new itemization it still won't be so hard to kill him. Element of comparison : Rammus W gives him up to 120 bonus resistances. Also you have to stay inside the circle, making Nasus fit the identity of a zone control juggernaught that stands his ground.

At 500 stacks, Nasus Wither now also grants him %damage reduction on the target equal to the attack speed slow (max rank 17.5% to 47.5%, for an average of 32.5%).

This will give him the edge as a duellist crusher and will make his Wither more threatening as a DPS-disable tool, indirectly buffing his teamfight potential if he puts it on a carry, so that people would be more encline to cleanse/QSS/Crucible it.

At 1000 stacks REMINDER : with how weak his earlygame now is and how long it takes to reach it even by freefarming, Nasus should NEVER be allowed to reach that amount of stacks.

Nasus skins darkens and becomes tougher, granting him permanent 15% damage taken reduction, 25% Slow resistance and 25% Tenacity.

Nasus will finally reach his form of a tougher tank/bruiser, with some "unstoppable" aspect (the slow resistance/tenacity). But tbh, he won't be unkillable at all, it just takes 15% more time to take him down (well there is also the bonus resistances from E, but he will be pretty much as tanky as a tank, not more, less than some. And god knows that tanks are fairly killable in end game.)

Some facts : Nasus damage is not amplified in any way, until he reaches 750 stacks, where the scaling (+5/+10) outscales the old one. This focuses on making him harder to take down. He is still rather kiteable and possible to take down, it's a bit harder but not at all to the point of making him an unstoppable 1v5 machine (tbh, still not sure he can survive some 1v2 combos, like Vayne + Nunu, Jinx + Nautilus for examples).

I would like to hear your thoughts about that rework, and possibly you own ideas/ concepts about what to make Nasus / if you believe he's like he should be, etc.