The ODE will require a software exploit to set up, for what it's worth. That doesn't mean it's any harder to patch, though. The ODE hardware itself isn't really a hack. Also what's this about the kernel exploit being removed in 5.1.0? I've seen no evidence of this.
They did this on the Wii, too.
Some of the other consoles ODE's have brought unsigned code to the table. Sure a software exploit may be required initially just to install the backdoor, but once its installed, it won't matter if nintendo patches the exploit once the backdoor is installed though
As for the kernel exploit, I tried finding the thread in regards to that, so I think I'm mistaken lol. Taking a look at the Wii U hacking discussion, makes my comment about that null and void