Malice was the word I was looking for. Good catch.
He did try to name Jaime in the Vale in the books, and like the show he was denied naming an absent champion.
I dunno, I think it would be a smarter move to name Jaime than the greatest fighter in Westeros. He wouldn't be naming a champion who he thought could win, he'd be naming one he thought couldn't lose, i.e Tywin/Cersei wouldn't match him up against someone who'd kill him (or would she?).
IIRC, tradition in the few trial by combat instances I have read so far holds that the accuser names their champion(s) first. Jaime is the only member of Tyrion's family that he has any attachment to, he would not send his brother into battle against Gregor with only one hand.
Why are we even debating the nuances of something that can't/ won't happen?
It can't won't happen in the books, but it could in the show. I don't recall any such nuance, but the episode in the vale did involve the accuser naming a champion first.
It won't. The god damn title of episode 8 is "The Mountain and The Viper".
This trial also involved the accuser naming their champion first. The same also applies to the only other instance of trial by combat in the stories, trial by seven from the Dunk and Egg novellas.
I'm not saying that it is Westerosi law that the accuser names their champion first, but it seems to work out that way. People are usually hesitant to volunteer for the accused's cause without knowing what they are going up against first.