Thoughts about maybe improving Singed? (theorycrafting really but curious)

Okay, so i'm relatively new to League only level 22, so you know i don't exactly know balance like the other better players, but in my opinion singed is lacking a little and it sorta makes me sad because he's so cool and fun, and his kit is strong, buuuuut in my opinion his game play is not. soooo i rattled my brain thinking "if i could improve Singed how would i do it?"

First of all i think his Q and E are fine as they are, they're solid (in my opinion >.> once again i'm new feel free to correct me)

His W, Is good sure, Buuuuut feels like, combo with E or go home crying, and his ult i feel you could actually make a little weaker and replace the W with it.

But then i was like.... "But then i've got to think of a Ult..." then I remembered reading in Lore about a noxian invasion and Riven called out for aid and Singed basically nuked it with biochemicals. So I thought that actually would make an interesting ult. Now i'm not sure about numbers so i'd leave that to you so i don't make it stupidly OP or a useless ult. But what about, an Aoe DoT that scales in damage the longer an enemy stands in it? because you know, the more chemicals you breath in the faster you die. As I said, absolutely no clue about numbers but it's an interesting ult, that singed could actually use in team fights. it could synergise with Allied crowd control. It could help zone enemies. and i think Singed's problem is his team fighting is, hope not to die while you run in and hope to flip someone then run away.

So What do you think? Ult moved to replace W but toned back a bit so he doesn't have two ults. then change his ult to some kind of AoE DoT that scales in damage = to the duration the enemy spends in the area?