There are a number of funders considering litigation strategies against the stackers. There are several elements that need to be in place for it to be successful. Notice to the stacker, UCC-1 language, and contract language with the merchant. The claim will be tortious interference.

I agree with others that ISO's will not be sued, unless they are actively participating in the stacking and the funder has no relationship with them. It doesn't cost anything to name another party in a lawsuit.