Pakistan is Islamic so they have skin in the game. There's no reason why China can't be friendly with both like Russia is.You won't get closer relationship with Sunni countries unless you show you are willing to pick them over Iran. Remember, your top ally Pakistan also has a problem with Iran.
Iran supporting proxies one of the underlying problems, just like Gulf states being pro-western and showing indifference to Israel.It doesn't matter what the underlying issue is. What matters is that Iran is engaging in proxy wars to further shiite influence in the middle east. These proxy wars have been very damaging for GCC countries. They have shown themselves desperate for attention from the west while not appreciating what China had done for them.
Bringing the Yemen war to an end was a big step towards that Now the same needs to happen in Lebanon, Syria and Iraq.
It may seem far fetched, but countries that were historically enmities do sometimes go on to become friends. UK France, Germany & France, the Scandinavian countries.
You could be right, although with nuclear capable ballistic missiles you can understand the reason for secrecy. Arms deals involving fighter jets, tanks and other weapons are usually not a secret.how many military deals between China and Saudi Arabia have been made public? Did the DF-21 deal get reported? We will find out in a few years what they've actually concluded.