I find that finding links between texts is really easy for me.
In the end, for related material, it depends on how much i'm familiar with it and how strong the concept is.
Your thesis should connect all of your texts in a very profound manner anyway
I think it's a great idea (even I don't do Belonging). I found it to be a good genre for "Journeys" because it's a linguistic text, allowing you to analyse language techniques, but it still gives a good contrast in an AOS study because of it's non-fictional/ prosaic manner. Only thing is, I would focus on maybe one chapter of the biography. Doing the whole thing will just be too big and too dilute - you won't have enough space to cover it comprehensively, so I'd just just focus on a selected, particularly pertinent excerpt.
Theres nothing bad abot doing a biography...its just another text form...the man thing is to have difernt text types rater then all novels,all movies etc. Biographies can be really good if you analyze hem properly.