China have full access to much of the Middle East through the oceans (Maritime Silk Road):
Much of the Chinese economic activity is concentrated to the East tapping the Maritime Silk Road (port locations). CPEC offers another channel for the same but not a requirement.
https://www.researchgate.net/figure/Map-showing-the-Eastern-Central-and-Western-regions-of-China-left-the-SEZs-and_fig5_271659102
https://www.researchgate.net/publication/328206059/figure/fig3/AS:680356697100288@1539221085308/Four-major-economic-regions-of-China.png
Economic activity in the Western Chinese provinces is substantially lacking in comparison because land transit is slow and expensive.
Point is in regards to
how Pakistan can capitalize on CPEC to its advantage without exposing it to a new round of sanctions via dealings with Iran which are prone to international sanctions.
China is an economic powerhouse and can afford to take RISKS through BRI given the span and reach of this initiative. Even if a route or two are sanctioned/suppressed, China can manage through other routes.
Pakistan have a much smaller (struggling) economy and is pinning much hope on CPEC to mitigate this problem. Therefore, recommended Foreign Policy approach is to PLAY SAFE and not take unnecessary risks in the process. Pakistan can convince GCC states to utilize CPEC and contribute to Pakistani economy in this manner - much better than tapping Iran for the needful in the present.
China is offering an alternative routes to Iran and CPEC is not a requirement once again.
As I have repeatedly pointed out in this thread, Pakistan should OBSERVE
how the next American administration will deal with Iran. Perhaps Trump administration will have a second term?
Just play it SAFE for now.