Placement of stative verbs
First of all let me point out that in Chinese the term &quot;stative verb&quot; 状态动词 is commonly associated to what you call intensifier, on this website too, for example here.
In English though, stative verbs are verbs that describe a relatively unchanging state, so we can include your examples, as 喜欢，希望，etc.
As for your questions, this is how I interpret the whole thing:

Why does 喜歡 precede the location-phrase 在圖書館？ (why not 我們 在圖書館 喜歡讀書 )

Because what you like in this sentence is the entire thing of reading in the library. If you invert the order, 我們 「在圖書館」 喜歡讀書 then you say that in the library, we like reading (i.e. when we are not in the library we don't like reading anymore).
Same as in the other example:

她希望將來當工程師

She hopes to be an engineer in the future (someday), and not, 將來希望當工程師 in the future, she will hope to be an engineer.
The state described by the stative verb applies to what follows. If you move complements before it, it doesn't apply to them anymore.
And finally:

On the other hand, intensifiers are allowed to come before the stative verb:

because they work as adverbs here, and modify the intensity of the described state:

我超级喜欢 I extremely like
我很喜欢 I like a lot (very)
我不太喜欢 I don't like too much (not very much)
我非常不喜欢 I extremely dislike