On the other hand, if you have a good picture of how the firmware works, it would be easier to imagine how a wrapper program for executing user-code would have to be written, and where on the hdd the modifications might have to be made. And maybe if we can make a program like that, inserting it into a firmware might not be necessary..
...just speculating. Because, I mean, expecting someone to write new routines into the firmware, that's a tall order. It's not a phone with a simple certificate check, or anything like that.
..yes and no. Like people say, the exploit doesn't give us much as users. It's a long way off before any custom firmware anyway.