Question

Hello Rabbi,
Recently I heard a news report:

Foreigners will be able to purchase real estate throughout Saudi Arabia.
In Islam's holy cities, Mecca and Medina, purchases by foreigners will be limited to Muslim foreigners (I should mention that in order to become a Muslim, it is enough to say the shahada before one witness — a quick and easy process).

A question occurred to me: would it be permissible for a Jewish businessman to say the shahada ("I testify that there is no god but Allah, and that Muhammad is the messenger of Allah")? I am asking from two angles. First, would it be permitted to deceive the seller and pretend to be someone converting to Islam even though I am not really converting? And second, from the Jewish halakhic perspective, is it permissible to say the shahada? Is there any aspect of idolatry in this?
 
Best regards,