Thank you CrazyRocky, I’ve since learned that both PTxPrint and SAB have the ability to replace the default numerals with a preset numeral system from another script. Interestingly, the SAB list of preset numeral systems is smaller than the PTxPrint list.
YouVersion will also display different numeral systems for chapter / verse numbers, but their process depends upon the \cp and \vp # \vp* being in the text. It’s also been suggested that I try using a change file in the project folder to insert them programmatically. I’ve not got any real experience with that so I will have to experiment. The end result has to be something that YouVersion, or any other DBL consumer, can use to display the appropriate numerals.