I prefer to only comment on the kit of a champion, because lore can always be ironed out whenever, but for something to fit into the game the kit needs to be done right.
I will say it is hard to make judgements on the kit without knowing his cooldowns. Only his passive and Q have them.
Morgan has an obscene amount of up front burst. His passive means that you lose effectively 50-75% of your health right away, the movement empowered auto on his W alone would likely be enough to either instakill a squishy or leave them one auto from death, plus it slows, plus his Q either punishes you heavily for staying near him with MORE high bases and scalings if he gets the jump on you or slows you down so heavily you have no chance to escape and he just chases you down with auto attacks.
You say he has no escapes lategame so he would want to build tanky. I don't think he would ever want to shift to anything further than maybe a ga/ other resist item. His Q and W are both aoe nukes that have slows attached. He would be able to make his way around the map rapidly with the coils so his global presence would be enormous, moreso than reksai with her old ulti if he just plopped a coil down at his fountain.
The passive is fundamentally unhealthy. Either the enemy wards the crap out of everything and the passive is useless, or they are unaware and he just squats in a brush while they get set up to lose the majority of their health. In a vacuum the passive isn't gross due to the delay on its damage. But combined with his crazy up front burst it means that no amount of healing or shielding is going to save you if he has a full stack passive on you and presses q and w. It's like seeing a karthus ult when you're low except you're not low and there's still not much you can do to stop it.
It also encourages the player to not actually play the game, instead
Can Morgan move while channeling Q?
Does his coil spell have a duration? Or a limit to how many he can place on the map? That much mobility alone would need to consume a lot of power budget.
His ult should just do the %damage itself rather than do all this interaction with his passive.