[user104658]

Diplomatic immunity is important for the reasons bots has stated and its important that the HOST country can't over-ride immunity, because of the risk of corruption and false charges.

However, I think it should be expected as a matter of etiquette that when it is a genuine crime or legal issue, the diplomats country of origin waives immunity and proceedings go ahead.

Best of both worlds then as it removes the risk to the diplomat from the host country, as the ability to arrest / pursue charges would always have to be triggered by the diplomat's home country.