While such a scenario was proposed by the Joint List, it is not currently considered by any of the other parties included in it.
In general, the ultra-orthodox and the Arabs are concerned with completely different interests, so their red-lines don't conflict at all. The orthodox are interested mostly with the continuous funding of their voters (Yeshivas, high child allowances) and religious aspects of the public life, such as public works and trade on Saturday. The Arabs are interested in promoting the economic state of the Arab population, fighting crime in Arab towns and villages, and moving the political process with the Palestinians forward. So in theory, they can support any left-wing government that includes the orthodox parties.
Edit in reply to comment:
Yahadut Hatorah has no interest in the West Bank, except maybe the few Haredi settlements, most of which are just across the Green Line (1967 armistice border). Shas is more right-wing inclined, but will likely agree to a withdrawal if they are convinced it is a real and viable agreement.
Such a cooperation isn't considered because the orthodox know they'll get what they want/need from Netanyahu, while with Kahol Lavan they'll have to give up much of their achievements. So they rather stick with him, as long as Kahol Lavan can't create a coalition. When time comes that they need to choose between the opposition and joining Kahol Lavan, things may change.