So many people are like you, they don't want to buy, just want to know how the tragedy ends. LOL
I've heard that many people stop collecting Graprara at volume 11 (chapter 98-107) which is a smart solution. So, volume 12-14 never exist for them. No one collect the volume they don't want to read it again, right? LOL
IMHO, the only win-win solution for everyone is to revise the chapter 129 "just" for making the volume 14.
Airi Katsura (sensei) already generates substantial revenue from Karami Zakari but Keishi Nishikida sensei likely relies heavily on volume sales from Grapara and would presumably be willing to make adjustments if doing that could revive sales for volumes 14 and 13.
Kodansha have no right to change the original chapter 129 but they can reject making the volume 14 or even take legal action if they can't make the volume 14.
Kodansha has full right to force AK (sensei) to change the chapter 129 just for making the volume 14.
So, the chapter 129 in volume 14 can be different from the original chapter 129 like the manga and its anime version have different endings.