Default [Q] Going back to stock without RUU?

I'd like to revert my Rogers HTC One back to out-of-the-box stock for warranty reasons, I'm currently S-OFF, bootloader unlocked (tampered flag removed), hboot 1.56, latest firmware 4.06. I need to go back to a locked bootloader with S-ON but there is no Rogers RUU in existence (I've read that if I S-OFF using another RUU I will brick my phone, not what I want). Is there a possibility to revert to stock or am I screwed without an RUU?