You seems to have misunderstood what I was saying (I was unclear of the dynamic of our populations sentiments; and how external event can threaten our internal security)
A sectarian war could arise not at the behest of the Iranians, but a ground swell amount some Pakistani Shias if Pakistan takes part against Iran, and a ground swell among some Pakistani Sunnis if Pakistan supports Iran. Down the road, these two nations may fund factions in our countries if we look like we are going down the line to becoming another Iraq (If we weaken our internal cohesion; other may exploit it). The government of Pakistan started a good policy to Back Saudi Arabia for its territorial integrity and defense within its border stance when requested to join in Yemen against the Houthis, and also choose to not join that war in Yemen. We drew a line to how much involvement was in our interest. Pakistan's "establishment" needs to be strong and prevent and/or repulse any efforts to fight this cold war on our soil. To maximize the chance we are not pulled into this cold war, we should stay out of it unless our interests are threatened or the terms of our security commitments are exercised; such as an Iranian direct attack upon Saudi Arabian soil. In which case, we could destroy or blockade those assets directly attacking Saudi Arabia, such as using our navy to protect Saudi Ships near our coasts, flying fighter escorts with our F-16s of Saudi Awacs (remember our F-16s held their own up against Euro-fighters, so they are as good as any to provide fighter escort), or sending a armored division to the Saudi-Iraq border to defend against an Iran armored assault via Iraq. We could also use our Submarines to keep an Eye on Iranian naval activities; and if they are threatening Saudi oil convoys. There are many ways our unique position allows us to support a DEFENSE of Saudi Arabia without sending divisions upon divisions of tanks to the Iranian border and sending the wrong signal.