How about letting the people take the lead in changing the system. It won't be what other countries would like to see, but it will probably be a lot better than the experiments you mention.
However, Al-Saud family was heavily financed and armed by the British during 1900 onwards. People's allegiences were divided among the Sharif of Mecca Hussain bin Ali, the House of Rashid, the Ottomans, and the Al Saud-Wahhabi alliance. It is not hard to imagine that these forces would have evolved in different ways during industrialization, post-Colonial and Cold War times.
Besides, there have been external forces at play to further or curtail the direction Saudi affairs are going in during the times of King Saud and King Faisal respectively. So it is not as if the people have necessarily chosen the kingdom system of Saudi Arabia while the West has installed democracies.
While not democratic, I think Sharif Hussain of Macca, the Ottomans, and to a lesser extent King Faisal of the Al-Saud would have moved things towards a more representative system. King Faisal's efforts brought women's education to Saudi Arabia and added a little (if only a trickle) to scientific education in some countries in Africa and Asia through student financial aid programs.
So there are various contradictory forces at play locally and globally and nothing stays constant.
This treaty (and the subsequent Treaty of Jeddah in 1927) legitimized their control over their territory and allowed Ibn Saud to go on to create the Kingdom of Saudi Arabia in 1932.
The Arab people had no part in the creation of the Saudi state. It was created by conquest combined with the support of foreign powers (the United Kingdom).
https://en.wikipedia.org/wiki/Ibn_Saud https://en.wikipedia.org/wiki/Treaty_of_Darin