It isn't viable in the sense that you shouldn't get it over the items you want to get. There is no place in your build for Essence Reaver and you aren't really mana hungry tbh.

Kog'Maw can harass from afar and seriously can outdamage Jinx. Successful flame chompers isn't a guaranteed kill, but instead you might outposition yourself and get killed by Kog'Maw and his support. Kog'Maw lane is at the very best skill matchup.

Yeah, but that doesn't make double Doran's Blade necessary. You don't necessary need that life steal before building a life steal item. I myself have no need for that little bit of life steal from the another blade if I am ahead because I know how to trade efficiently and I have Feast

If you need warding you buy wards. Simple as that. Blue trinket can also reveal enemies doing baron/dragon, camping in a bush and possible skirmishes.

Essence reaver is not as good as bt/botrk, but I don't see how it's not viable.
I don't see how kog has an advantage vs jinx in lane since she outdamages him and a good flame chompers is a dead kog'maw.
Double dorans gives you the lifesteal you need before building a lifesteal item.
The trinket you pick in the late game is a personal/situational choice in every game. Sometimes you need warding, sometimes counter warding. I don't see the advantage of having blue trinket other than revealing people so you can ult them, which is not necessary and not worth it.

Essence Reaver is a no

you don't necessarily need two Doran's Blades in every game

In the late game you want to have blue trinket, not yellow trinket

Kog'Maw has an advantage when laning against Jinx

Anyone can dodge your abilities even though you state they can't in the matchup section. They can, you know, walk.

I wouldn't mention Essence Reaver at all as an option.