How to create dynamically-selectable Lorawan region / channel selection at startup

[pomplesiegel]

I made this as a github issue before, but now I realize perhaps it is better suited for discussion! Any thoughts?

For a device which could be used in many regions across the globe (assuming a corresponding variant of modem + antenna is installed), what is the best way to programmatically select a pre-defined channel plan per region at startup?

The goal is to avoid having unique binaries for each possible channel plan (adds up very quickly once you consider all possible global regions). I see how to make this change in code, but this would produce unique binaries for each region.

#define CFG_us915 1
//#define CFG_au915 1

This is what I imagine for a workflow:
Device starts up and reads from dipswitch / jumper configuration values to indicate what region it is in and what modem is installed
Device programmatically loads appropriate channel plan into LMIC and begins normal LoraWAN join behavior
Any thoughts? Forgive me if this is an obvious question.

Thank you,
Michael