Hi Dom,
Not sure that I correctly understood your questions, here are a few answer elements.
1. I have no idea if complete_your_profile works with Moodle 2.7, I didn't test sorry about that. But it should, as it involves only simple mechanisms (a few SELECT in the database).
2. Unfortunately it doesn't fix any core code, it's just a plugin that adds more code.
3. This block shows a message and a button in the block region where you added it. The button takes the user to his/her profile page and does nothing more. Unless the profile page is "complete" (according to the block options you chose), the message and button will keep appearing. But it doesn't force the user, it just suggests/advises to complete their profile.
Hope I answered your questions,
Greetings,
Mathias