From the first missile fired their locations will show up on Saudi ground radars. Then a SEAD mission with storm shadows and AASM and pave ways and GBUs followed by complete neutralization of Missile threat in the first hours then Iranian ground forces are open game.
I have read extinsenvly regarding this subject and I know what I am saying.
If the USA talks about hollywoodie scenarios that makes sense, but Saudi Arabia?
I doubt your radars would cover even central parts of Iran to the precision that it wants to track Iranian missiles inside the Iranian territory, let alone eastern parts of Iran. so we can easily launch missiles from eastern parts of Iran to any point of the Saudi territory that we'd please.
Iran has portable launchers, Iran has hundreds or thousands of solid missiles that can be launched any time just by pressing a button, Iran has tens or hundreds of secret missile silos loaded with missiles in them under ground. Before Saudi Air force can even gear up the Saudi air ports are flattened, and as far as I know Saudi Arabia doesn't have F-35 that takes off vertically or anything close to that, so once the air ports are damaged the Saudi air force can't do much. Moreover, our radars are fully capable of detecting all of your air planes, so you'll be prune to our anti-air craft systems.
Saudi air force is lethal and it's way superior to IAF, but it doesn't have the ability to take the advantage of air superiority over Iran, because 1: your air ports all are prone to our missile attacks. 2: you can't get deep through Iranian territory with your air planes 'cuz they'll soon be detected and targeted. (remember the sentinel drone incidence?)
Moreover, you think Iran only produces surface to surface ballistic missiles? if that's your idea about Iranian military you're wrong my friend. We produce precision bombs that can be dropped on target from +50 kilometers away with our F-4's (I guess a better number is 80, but I'm not sure, I'm having memory problems now), we produce cruise missiles, we're trying to reverse-engineer phoenix missiles that could be lethal for any aircraft in the Saudi air force if they're launched from F-14 and there are claims that Iran has already produced a similar variant of phoenix missiles, we produce anti-tank missiles and we're trying to build something similar to Javelin in the near future (at least close to that), we produce howitzers, we produce frigates, we produce submarines, phased-array radars, etc...
Have you ever thought how you could contain Iranian navy? (I exclude Iranian ground forces because both countries don't border each other directly)