Getting back to relevant topics;
Starfox Zero appears to require, at minimum, a 5.5.1 spoof. Inserting the disc prompts a System update. I'm lead to believe that means that the game has the 5.5.1 update on disc, but can anyone confirm this? I updated my main Wiiu to 5.5.1 via the internet (regrettably, I did so before picking up Star Fox, or I could answer my own question), but my spare is at 5.0.0 and stored away.
I have an original release Splatoon, so I can get to 5.3.2 easy, but I would sleep better knowing I could get to 5.5.1 via disc if Nintendo ships a newer firmware (which I have to believe they will try with the new Link title, if not sooner).
Reiterating my question for those who didn't read the above: Does Star Fox Zero have the 5.5.1update on disc?