That's a very good point. Mobile OS vendors should allow for user-defined search engines the way that desktop browsers do.
Of course since one of the options in Safari is DuckDuckGo, you can also use its extensive list of !bang operators.
I’d prefer a static list for those people.
I could write a book on the crazy stuff he has done to his iOS devices. I’ve contemplated putting “child mode” or whatever on his account to prevent him from changing settings or installing apps.
My favorite so far was a malware VPN that was harvesting ALL of his traffic.