Arabic Transjordan and Zionist Cisjordan may have been the original two-state solution, but it's not going to work now, even if it ever could have.
Thats always been a naive idea. But a Palestinian state on both sides of Jordan could work if the monarchy were replaced with a democratic republic controlled by the Palestinian majority. It will take a revolution in Jordan of some kind to achieve it, but it would change Palestine from a quasi-state squeezed between hostile Israel and suspicious Jordan to a viable entity with some control over its own destiny. Hard to see it happening, but that goes for all possible solutions to that particular coflict.
Seeing as the Jordanian monarchy is one of the stabilising factors of the region, it seem rather counter-productive to replace it with a Republic. Beside that the Jordanian including the descendants of the Palestinian refugees has shown little wish for a reunification with the West Bank, as such I find it rather mean to force such a union on them. In fact the major supporters of such a plan are among the Israeli (because it would leave someone else to clean their mess up), it have little support elsewhere.