The peace treaty between Israel and Egypt restricts the number of troops allowed in the Philadelphi Corridor and Sisi is adamantly against Israel bringing in any more troops to that area for fear that that would push the Palestinians into the Sinai. If Israel goes ahead anyway Egypt could nullify that treaty and send troops of their own there to confront the IDF opening up another war front Israel would have to fight against. This at a time when they are about to engage Hezbollah in the north. How many fronts can Israel handle?
I believe that Israel has gamed the invasion of Lebanon ad nauseum, and for decades it has planned securing the land south of the Litani River.