I think it is likely true that red lines will not work, first, because I don't think the US has the will to suggest them and if they did, Israel would certainly not have the will to accept them. Nevertheless, rational and fair minded red lines could usefully band world opinion around a single solution. The '67 borders are no longer workable; Israel has seen to that with its forever building on occupied land. But the '67 borders with reasonable modifications to insure defense and appropriate land swaps to assure a viable Palestinian state would serve as a goal to strive for. A fair division of Jerusalem would also be a useful goal for the world to stand behind. It is true, ideals rarely work, but they are worth keeping an eye on and striving for.
Colombia recalls ambassador to Venezuela amid border crisis (Reuters)
from the article: Abbas to U.S.: Peace talks won't work until Israel given red lines