:I'd like to see this discussion move toward closure instead of spiralling out of control, but I'll respond to your most of your points. 
 # The way that things like the potential confusion between "tea oil" and "tea tree oil" are normally dealt with here is by adding the  template at the beginning of the article. Something like: 
 #: {{dablink|This article is about the essential oil derived from plants of the genus Melaleuca. For the oil derived from the tea plant, see [[tea oil]].}}. 
 # It's interesting to note that all of the links to versions of this article in other European languages use names that are related to "tea tree oil", not melaleuca: Teebaumöl (German), Theeboomolie (Dutch), Teepuuöljy (Finnish). As for whether one is more common than the other, a Google search for the two phrases show nearly 1.3 million results for  and about 30,000 results for . I know that a Google search isn't definitive for worldwide colloquial usage, but according to this metric "tea tree oil" is 40 times more common. 
 # English Wikipedia is targeted at English speakers. The article already accomodates non-English speakers and those who only know the name "melaleuca" by providing a redirect from melaleuca oil and by calling out the alternate name in the first sentence. 
 # Tea tree oil doesn't have a scientific name. The plant it's derived from does, but Wikipedia convention generally doesn't name anything with scientific names except species of plants and animals. 
 :I realize that you think changing the name adds value for a global perspective, but readers using names other than "tea tree oil" are already accomodated by the existing redirects. Someone searching for "melaleuca oil" or linking to it will find this article, not to mention the redirect from tea tree oil (melaleuca oil). There isn't really anything gained by having "melaleuca oil" in the title that isn't provided by having the alternate name in bold text in the first sentence.