Please don't give the writers too much credit. T'Pol's addiction was just an excuse to make her another f'ed u p woman, like Kara Thrace. It was a way to get around Vulcan sexuality, make her angry and available at the same time in a way that was inconsistent with the character.
Let's hear from Frau Blalock: None of these quotes directly reference a producers' decision. They do reflect the actress' understanding of the development and how outside the character's development it was. Moreover, it links, implicitly, the addiction and changes in the character's sexuality, which the actress felt lacked continuity with the character's development.
But do you have anything that says that it was done with the intention o turning her into "another f'ed u p woman... a way to get around Vulcan sexuality, make her angry and available at the same time" without regards to the character?
You are asking me if I have a source for my critical assessment of what happened to T'Pol? That would be me. Do I think that Braga and Berman literally wanted to make T'Pol damaged goods in order to get a sexier T'Pol? No. However, I believe that was the end result. The actress' observations and feelings reflect her own understanding of the character and her relationship with production, but nonetheless act as a type of evidence. While Blalock doesn't name names, she points out serious discontinuities in her character, about which I feel free to analyze. Moreover, I think that this fits into a pattern, in which formerly strong women whose emerging sexuality parallels the rise of psychological conflict. Was the Trellium-B plotline necessary to make T'Pol more sexual or more romantic? All that was necessary was time, particularly more exposure to non-Vulcans. Did the Trellium-B plotline enhance our understanding of addiction through the lens of science fiction? YMMV.