I was looking into some of the older champs that I DONT want large work to go into and made me think of Amu.
The first issue I think he has is that his W and E share the same purpose.. and since W is shared with so many similar champs (hecarim, karthus, mundo) what can be done is to combine the two into a trigger that pulses out bandages increasing its potency, helping early clear with less mana cost.
Idea for W is for Amumu to cast W (similar to live E) and after each cast he gains an aura that increases in size and damage as he throws more and more of a tantrum up to 3 times; he will still have the cooldown reduction based off AA.
That leaves me with his E, just a placeholder for a more creative spell.
I had an idea that his new E can be:
Tainted love (placeholder name):
This send out a spectral version of Amu (works like spooky ghost) and targets the nearest enemy champion and black outs any wards it passes through and gives Amumu a MS bonus towards the champ effected.
Champions also marked by this effect causes them to shoot out a bandage towards the direction that Amumu uses his bandage toss, if they meet the champions slam together and do increased damage.
R: additionally each champion hit has the same effect as being hugged by his specter so u can follow up your R with a huge Q.