Personally I wouldn't touch it with a barge pole. Not because of the fabric but because there are far more things that can go wrong with it than can go right and it looks to me like a nightmare in the making. Sometimes the smart thing to do is say, 'thanks, but no thanks.'
Sometimes you look at a job and alarm bells are ringing in your head, often those alarm bells are linked to a job you did years earlier that you really wish you'd left well alone, because by taking on a job that is already problematic you also take ownership of those problems and become responsible for any others that may come about as a result of cleaning.
If the customer will sign a disclaimer, then that's different.
Just a thought.
Simon