I've got my code pretty much done (in theory). I haven't yet flashed the Pro Micro and tried doing anything with it yet since I don't have any inputs or outputs yet wired up. I'll take that on next. The code ended up being a bit of a challenge because, rather than going the easy-yet-inefficient route of creating separate functions for each button with a great deal of redundancy between them, I decided to create a 2-Dimensional Array instead. Problem is, Arduino apparently doesn't actually support multi-dimensional arrays. BUT it does support Arrays of Arrays! So that's what I did.
I also came up with a name to go along with the NAG acronym (since I'm pretty sure my family wouldn't appreciate me calling it the NAGBox, yet I still want to). So, this is now officially the "Notification Alert Generator Box!"
Next step is getting the power situation figured out, (the Skywire cellular modem and Arduino run at different voltages) and wiring up a Proof of Concept so I can test my code and then figure out why it didn't work.