Very often the Trilemma argument is treated as a proof of Jesus's divinity. I'd like to see how far it can go, not as a proof of Jesus's divinity, but simply as an argument against the claim that Jesus was a great moral teacher but not God. Whatever other options may be available to us (myth, legendary accretion, mentally ill genius, crackpot eschatological preacher, etc.), does it refute what it is primarily designed to refute, that Jesus was a great moral teacher who tried to teach us to be nice to each other, but the theological claims made concerning him in Scripture are just wrong.
Given the fact that our only sources for Jesus say that he did and said all sorts of things that imply that he was claiming to be God, the idea that he was just a great moral teacher but not God is does seem absurd. Either he was right about all that (in which case he would be God), or he was lying about who he was (in which case he would not be anyone people would want to follow) or he was nuts. If you can't accept him as God, then you can't follow him as a moral teacher. As Lewis put it:
"I am trying here to prevent anyone saying the really foolish thing that people often say about Him: I’m ready to accept Jesus as a great moral teacher, but I don’t accept his claim to be God. That is the one thing we must not say. A man who was merely a man and said the sort of things Jesus said would not be a great moral teacher. He would either be a lunatic — on the level with the man who says he is a poached egg — or else he would be the Devil of Hell. You must make your choice. Either this man was, and is, the Son of God, or else a madman or something worse. You can shut him up for a fool, you can spit at him and kill him as a demon or you can fall at his feet and call him Lord and God, but let us not come with any patronising nonsense about his being a great human teacher. He has not left that open to us. He did not intend to. ... Now it seems to me obvious that He was neither a lunatic nor a fiend: and consequently, however strange or terrifying or unlikely it may seem, I have to accept the view that He was and is God."
Now you can back out of these claims by saying that the Scriptures aren't reliable historical records and that Jesus never did or said anything to suggest that he was anything more than a Jewish carpenter with a call to preach. But if the Scriptures are highly unreliable about who he claimed to be, how could they be reliable when it comes to identifying what he taught?
We can call the argument against the "great moral teacher" hypothesis the modest trilemma. In other words, we might ask if the argument is successful against the "nice-guy Jesus" that is often part of popular culture. The ambitious trilemma tries to get you to conclude, instead, that Jesus was God. Defending the modest trilemma will certainly be easier than defending the ambitious trilemma.