According to The Great War (the channel on youtube), after the discovering of a jewish spy circle that was giving information to the british the Ottoman authorities considered genociding the jews of Palestine and Syria in the same way as the armenians, but von Falkenhayn took steps to prevent that.
So the premise is that, for some reason or other, something similar to what happened to the armenians (death marches, massacres, etc) happens to the jews. Obviously it wouldn't happen in a scale even comparable to the Holocaust, but would surely effect public conciousness in some way. The answer is, inwhich one? Would be enough to diminish antisemitism (probably not on the same level as after WW2, bjt who knows)? Would the british authorities after an eventual establishment of the Palestinian Mandate be more pro-jewish? What could have happened?