That solution always sounds good ... initially ... and without further thought, by many supporters of Israel. Many times it’s prefaced with something to the effect that it all belings to Israel anyway.
But it turns out to be a TOTAL DISASTER upon further thinking!
The further thinking is this: Israel already has 20% of its population right now ... who are Arabs, and who have been given full Israeli citizenship BY LAW (Israel’s own law). They voted for their own Arab party this last election and are the THIRD LARGEST PARTY in Israel (with only 20% of the population). If Israel were to take over ALL THE LAND that they conquered in the war, that would mean another SIX MILLION ARABS in Israel, besides the 20% already there!
With those SIX MILLION additional Arabs, who now BY LAW have the vote (because Israel says it is not an Apartheid state, and that’s true) ... the nation of Israel would turn into an ARAB-CONTROLLED STATE and no longer be the “Homeland for the Jews”. It wouldn’t be long before the Jews became second class citizens in their “former nation of Israel”!
There are not 6 million Arabs in Judea and Samaria.
There is no demographic threat. This was a false canard raised by the leftists years ago in order to propagandize for the two-state solution, and it has been thoroughly debunked for years. See, for example, http://foreignpolicy.com/2013/12/18/israels-demographic-time-bomb-is-a-dud/ Nobody can accuse Foreign Policy magazine of being right wing, and even that publication admits that the demographic threat does not exist.
There may be realpolitik reasons why it would be difficult for Israel to annex Judea and Samaria, but Israel would face no internal threat as a result of doing so.