Your example just goes back to my original point. Psychological problems can be overcome, you state the depression is shown to be a chemical imbalance, and you say suicide is the ultimate expression of free will over ones own body/life. I challenge you to look at it from an alternate view.
To use your own example, the person has has maybe a year left or less before their social situation is likely to change due to factors entirely out of their own control. So instead of sticking it out and hanging on just that little bit longer, like they have been the past three years already, you propose they say "fuckit, this is to hard I'm out." Would it not be a greater expression of will to push on despite what their chemistry is telling them, to take it one day at a time if need be and at the very least just hang on that little bit longer, after all one year is a small time when the length of a full lifetime is taken into account.
You talk about suicide being an act of taking back control of ones life, it really isn't. Its ending that life. Its like pressing stop on a movie and then throwing it away just because one scene doesn't life up to the rest of what you've seen or been told about it. (highly simplified example I know)
Going back to your example, would it not be a greater expression of will to examine ones life, their day to day actions, the reasons other bully them, and then make positive changes. Better yet stop responding to the bullying, accept that some people are dicks and ignore them, they may escalate their bullying in the short term but if one continues to be unresponsive to that they will get bored and go pick on someone else.
also note that unlike the depression bit I am speaking from personal experience here, I think in my entire school life I had maybe 5 friends, over 13, not all at the same time. I was bullied daily, even beaten on several occasions. I responded to the beatings by learning a martial art, which in turn not only allowed me to defend myself but it taught me self discipline. I also came to the realisation that most of what bullies say is frankly out of ignorance and the desire to elevate themselves above others, even when the things they say have a ring of truth all it takes is a conscious effort to ignore them.
Anyway I've waffled on for longer than I intended, but I think I made my case.