I hadn't found it before, and I think it's something that could really help new people wanting to hack SMB, so I uploaded it here.
The init and bankswap routines come off of nesdev, and they're certainly simple compared to games I've worked with in the past, my own project has a few optimizations, but I wanted to keep the hack simple. I covered using them in the readme, also contains build scripts that would need pointed to the correct cc65 binaries.
If the hack is extensive, the hacker will likely have to shuffle some more routines into banks 1 and 2, but its all much easier to do via assembly than via binary, so I'm assuming the people wanting advanced hacks will have knowledge on how to do that.
Hopefully some of you will find this helpful.