I'm glad to see that someone's picked up the slack here

. I abandoned this project, but I'm happy to see others working on it

. As for initiating code execution, I think
Marionumber1 is right. Its going to take more than just redirecting to our own custom file to get it to run. The code won't be signed properly so the Wii U will reject it right away. My original idea with this would be to use corrupted image files to trigger an exploit to get the code to run (much like how black hat hackers, use corrupted image files to install and run viruses without the user's consent or knowledge on a pc). Except in our case, we wouldn't be doing anything malicious with it.
If we can trigger an unhandled exception using a corrupted image file, we might be able to tweak it for code execution. In theory, if we can trigger code execution within Smash bros, it "should" give us the same privileges that the game itself has (meaning sd card access

). We could then use this to launch simple homebrew apps off an sd card. Of course this would only result in a userland exploit so it would be limited, but it would be sufficient enough for basic homebrew apps (nes emulators, MAYBE some simplistic media players etc). If this exploit can be accomplished, someone could write code for a custom homebrew menu, that could be triggered with the exploit, that functions much like hbc on the wii/vWii and list all the homebrew apps on the sd card for the user to select w/e they want to launch. Of course, with a userland exploit NOTHING can be installed to NAND, but the menu could run entirely off the sd card.
I have a feeling if a userland exploit like this is developed, it would be extremely difficult for Nintendo to do anything about it (like with the original smashstack, heck it still runs on the vWii XD).