Sending Assisted GNSS (A-GNSS) to Bangle 2 GPS (AT6558)

the App Loader is the less complex solution

May be App Loader is the less complex and more optimal, but it requires manual intervention.
There are not too much code to parse and push the .bin to GPS.
And it can be automated. App, after it turns on GPS checks if it needs AGPS. It can be done with using $PCAS06,L*6, or just checking if no fix in 1 minute. Or checking if a bin file is there, but it is too old. If it is, then app downloads new file and pushes it into GPS.

In Espruino, there is just one thread.

I know, I am probably too spoiled by multi-threaded environments. :)
I am completely convinced not to halt the CPU.
I am reading about Generators and Yeld/Next. It looks like a concept of "yeld" in Windows to allow main loop to process messages and then return control back to a function.