That's really useful, thank you - and it tells me something I didn't realise. Your method repacks the game's APK because your mod is a modified SWF. Mine isn't: GL2MP is a separate AIR app that loads the player's own copy, and the AIR SDK builds Android APKs directly. So I'd ship my own app and never touch Lunime's APK at all, which also solves the copyright worry I had about Android.
Still plenty I don't know - how file picking works there, how it performs. But you just saved me from going down the wrong road. Do tell me when that YouTube tutorial is up, I'll watch it anyway.