Step 2: The Saudis allow Israel to establish a secret airfield in the desert.
Step 3: Israel strikes Iran.
Step 4: The Saudis publicly condemn Israel.
Step 5: The Saudis privately congratulate Israel.
I wouldn't be surprised if Steps 1 and 2 were already in place.
There is no longer any such thing as a "secret airfield". With the number of Earth Observation Satellites working today images of any supposedly secret airfield in Saudi land would be in the possession of many countries already, not to mention the US satellites which would be very capable and very interested in new construction.
But, if the Saudis allowed Israel to use an existing airbase this might work out well.
Both Israel and Saudi Arabia use US equipment. Fly the right aircraft to SA ahead of time and with a little repainting it might be possible to convince anyone looking at a satellite image that those are Saudi planes on the ground, not Israeli.
Or, a few extra temporary hangers and a lot of stuff can be kept out of sight. The boys over there know a lot about large tents.
Fuel and everything else can be supplied through the existing facilities.
As you say, step 1. is probably done.
Step 2. ready and waiting.
Step 3. Maybe a little different than yours. SA does not actually attack, but does supply cover for Israeli planes. Fake sorties, radar from planes over the ocean, etc.
Step 4. SA condemns Israel, denies allowing overflight.
Step 5. As you say.
The big unknown: Can this be done with missiles/drones/cruise missiles instead of aircraft?
The US Miltary sold 30 Super Bunker Penetrators / Busters to Israel last year.