No - it would never be allowed - it wouldn't be up to KC alone. Because security, confidentiality, trust, decorum, dignity, credibility. All gone for Harry.
But also - KC and Camilla have been vilified by H & M, and he's seen his heir, William and his brave, poorly wife, Catherine, absolutely taken apart by them, and by their attack dogs in the SS. I think the strain shows on William's face and frankly, if I was William and Charles agreed to a half-in, half-out arrangement, I'd throw in the towel and go and live a private, comfortable life in the country with my kids, like the Middletons.
Harry is not important to anyone now except to Charles as a father. It's on that private, very limited basis only that I think there can be any rapprochement.