How do you think this is going to work?
By the RAW accuracy isn't relevant for a ranged cleave "The chosen figure must be an eligible target" is the only restriction but the first quoted response I found on the issue says
" So, if Gaarkhan performs an attack with a ranged weapon and triggers cleave, the cleave damage can be dealt to any figure in line of sight and within the accuracy results of that attack."
(I was really surprised that this was about ferocity instead of dancing weapon).
The literal rules response is that the hidden figure is not defending so hidden doesn't apply but flavor wise it shouldn't be easier to hit someone hidden when you're aiming for someone else and ricocheting (or whatever ranged cleave is) and we've already seen the literal rules response be overruled on this issue.
I'll be sending a rules query 30 days after release if it's not faq'd by then. Until then place your bets, state your feelings or whatever else you like.