They would simply deny they knew he was going to lie.
They wouldn't recommend him to lie either, they would coach him on how to avoid the questions the prosecutions questions.
Questions are not hard to dodge.
If they are yes and no questions his lawyers will simply explain them in the rebuttal.
They can also work out questions to be asked and be put off limits before Trump were to testify.
Don't ask us this and we won't ask you this type of thing.
LOL. Questions are hard to dodge. Dodging questions in front of the jury makes you look guilty.
You can't put topics relevant to the crime off limits. They can't ask him what he had for lunch but they can ask him about every document in his possession and every conversation he had about those documents. They can also ask him about everything he has said in public about those documents.
Questions that show the jury Trump is lying
Did you have the documents?
Did you declassify the documents?
Did you say that you didn't have the documents? (Proves he knew he shouldn't have them.)
Did you say the documents were planted? (Proves he knew he shouldn't have them.)
Did you say you declassified the documents? (Proves he knew the documents contained national security secrets.)
Did you tell people you couldn't show them the documents because they were secret? (Proves he knew the documents contained national security secrets.)
Trump can't testify because his own actions and words will prove his guilt.
The defense doesn't get to bargain as to what questions they won't ask. They get to ask questions deemed relevant to the defense. The judge won't allow them to ask what the prosecutor had for dinner.