If Molag bal or any Daedric Prince for that matter ate a mortal would the mortal become a daedric prince like Malacath?

Malcath was created when trimac was eaten. trimac was not a mortal to begin with so no they wouldn't become a deadric prince.

That's what happened to Trinimac, though it was more a matter of Boethiah's intent to discredit him than anything to do with Daedric physiology. Also, the story may have been meant to be taken figuratively rather than literally.

The distinction between the et'Ada and the mortals was not so hard and fast in the past: the Altmer retain a memory of it, as recounted in the Monomyth: "Some had to marry and make children just to last. Each generation was weaker than the last, and soon there were Aldmer."

Not to mention the fact that the eating (literally or figuratively) was not required to elevate a mortal to the station of Daedric Prince in the Shivering Isles.

The COC isn't a daedric prince. At best, he is a powerful mortal who's assuming a temporary spot in place of a daedric prince. At worse, it's all just a dream/hallucination and the COC is trapped in a coma.

It's hard to say; the Daedra Princes can't be trusted to tell the truth, assuming they would share such secrets with mortals, and the Aedra, being shaped by myth, would just tell the mortals what they already or want to believe. Umaril was able to become partially daedric, although it was said he was half-divine beforehand.

No; he's just become the lead actor in a play, elevated from understudy status by the lead actor before him. Mantling isn't something so simple as to be a temporary placeholder. The CoC and Sheo have become indistinguishable by all means, and if they are indistinguishable by all means, they are the same. Identity property; A = A.

Eating is movement of a spirit to the sub-gradient, to avoid death during a kalpa turning. Thus, by being eaten, a mortal cannot become a Daedra.

A ridiculous assertion that serves no purpose other than to spark debates and confuse children.

At best part of Sheogorath's Madhouse detached itself and became Jygglyag, and the soul of the COC became mingled and dilluted by madness (∞-1=∞) and was so absorbed into the realm. The Shivering Isles wasn't Everything; Et'Ada are infinate.

Beings like Trinimac and his relatives weren't exactly mortals, nor exactly Divines in the strictest sense. They were the Ehlnofey. They were powerful ancestor spirits, who were in my opinion a sort of in between stage connecting the Divine with the mortal. I believe Umaril's father was one, as were beings like Morihaus the Bull and other figures of the past. These were the ancestor spirits who called the Dwemer "dwarves", because they stood on average at least twice as tall as modern races on Tamriel, and so their little Dwemer friends would appear as dwarves next to their stature.

Owing to his semi Divine nature, Trinimac's body and spirit were corrupted by Padomaic energies and he was reborn in a hideous form. Would this happen to a mortal? Well, we do know that spirits like Clavicus Vile and Molag Bal can claim the souls or mortals. What they actually choose to do with these souls is up for debate. It seems more logical they would torment them for amusemant rather than transform them into lesser Daedra, but it's possible since the mortal races are supposedly descended from the Ehlnofey, and in turn the Aedra.

Interesting take on it Hairdo, this would also explain how Umaril, having a divine father and mortal mother, was able to become partially, but not fully, Daedric. And why Malacath is weaker than the other Daedric Princes and not considered a "true" Prince by the others. And how Jyggalag changed so drastically when he became Sheogorath, while the CoC didn't change nearly as much upon becoming Sheogorath.

From what I understand, the Daedra and Aedra are labels to classify the various et'Ada; it appears that it is possible to change them so that they would fall under a different label.

When is MK when you need him?

Ha, I was always in the mindset that the CoC was just a temporary place holder for Sheo (I die when I fall from heights, Daedric Princes do not!).

Umaril's father was Ehlnofey? So does that mean Umaril is the oldest person in Tamriel?

Oldest surviving (part) mortal in Tamriel? Possibly.

I was always of the mindset that there were not degrees in such things. While he sits the throne in New Sheoth (however long that may be) the COC is Sheogorath. Can he make it rain burning dogs on Nirn? Of course not, but does that somehow make him not the sovereign of the Shivering Isles?

Perhaps it is a matter of perspective. To the other Daedric Princes the COC is probably held in lower regard than Malacath. To those who dwell in the Shivering Isles or on Nirn he might be looked upon as a Daedric Prince.

The other Daedra wouldn't be able to tell the differance between Sheogorath and Sheogorath: HE'S THE SAME DUDE

Mantling FTW. I guess. The point is that at the conclusion of SI, the artist formerly known as the CoC ceased to exist. Sheogorath is Sheogorath, and that's the only statement that has any meaning whatsoever. Now, Sheogorath now is certainly shaped by the artist formerly known as the CoC, and you can be damn sure that Sheogorath is going to be running around Cyrodiil saving the world and kicking Mehrunes Dagon's [censored]. But (s)he's still Sheogorath.

The important question is this; why would a Daedric Prince make someone a Daedric Prince?