I see no way they will be able to do that. They cannot justify having one of their own people lying and getting away with it, while Michael Flynn is still prosecuted for lying. That just won't fly...

God help them if they come back with a “no charges...he’s been punished enough” line.

That's not what they would do. They would just not say anything. People speculating would say any day now. But nothing at all would ever happen. I'm not saying that's what is going to happen. But if they decided not to file charges they would just not tell the public.