It's a challenge to be sure.
I think one option would be to have an "opt in" type of deal where the youth and/or their parents can elect to have someone else in the room. Or, the bishop provides the list of questions in advance so that it is at least clear what will be asked. I mean, they kind of do that for children's baptism interviews right? Perhaps if the youth were to know in advance what certain morality questions "meant" then there would be less confusion/misunderstanding/explanation needed.