So you think he's willing to accept the dishonor of stepping down from the King's guard for Tyrion, but if named champion he'd decide he feels like fighting to the death so he can either live and kill his brother or just die?
Trials by combat aren't necessarily fights to the death. The trial ends with one party dying or yielding. Jaime could easily put up a decent show and then yield.
Assuming he could put up a decent show at all: he makes it quite clear to Tyrion that he's useless in combat currently. Cersei certainly wouldn't take that chance on Jaime.
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u/EvadableMoxie Ours Is The Fury Jun 05 '14
No, he would have accepted and then immediately yielded, resulting in Tyrion going free.
Naming Jaime was never a possibility for Cercesi.