Why on Earth would you wonder about that?
You answered your own question.
They would love nothing more than Israel neutralising the threat, Of course, use of any Arab nation air space would need to be deniable.
Absolutely, which makes me wonder about this announcement, as it buggers the deniability aspect of the political game.
See this tidbit if for an illustration of what I'm getting at, skeptical wise ...
Saudi airspace 'not open for Iran war'
And
Israel denies Saudis gave IDF airspace clearance for Iran strike - Haaretz Daily Newspaper | Israel News
Israel denies Saudis gave IDF airspace clearance for Iran strike
PMO: Report is fundamentally false; Sunday Times: Mossad chief held secret talks with Saudi officials.
This seems to be response to the Times (LOndon) story that begins thusly:
The Times // June 12, 2010
Saudi Arabia gives Israel clear skies to attack Iranian nuclear sites
Hugh Tomlinson
Saudi Arabia has conducted tests to stand down its air defences to enable Israeli jets to make a bombing raid on Iran’s nuclear facilities, The Times can reveal.
In the week that the UN Security Council imposed a new round of sanctions on Tehran, defence sources in the Gulf say that Riyadh has agreed to allow Israel to use a narrow corridor of its airspace in the north of the country to shorten the distance for a bombing run on Iran.
To ensure the Israeli bombers pass unmolested, Riyadh has carried out tests to make certain its own jets are not scrambled and missile defence systems not activated. Once the Israelis are through, the kingdom’s air defences will return to full alert.
“The Saudis have given their permission for the Israelis to pass over and they will look the other way,” said a US defence source in the area. “They have already done tests to make sure their own jets aren’t scrambled and no one gets shot down. This has all been done with the agreement of the [US] State Department.”
There is enough blatant assertion in this to make me seriously doubt Mister Tomlinson is doing little more than spreading about a two year old rumor.
However, I leave open the possibility that the Saudi King is in on it, for the reasons you cited, and this: of the two evils, Israel is easier to deal with than Iran, for the Saudi King.