I'm a multilingual person from the Netherlands.
I think the use of 'rather' as a verb is common in Britain.
I certainly have heard the expression: "I rather you don't".
I always thought that the word 'rather' was used like 'wish' but today I changed my mind.
Speaking 5 European languages has taught me that etymology is the basis for most meanings of words and that going back usually teaches you why a certain word is used in a particular context.
This morning I decided to find the overall meaning of 'rather' (and that's how I found this page).
One of the explanations of the meaning of 'rather' is something like 'with ratio'.
It means something like 'with thought' or 'after (some/any) thought' or 'I conclude'.
Note that this meaning can be substituted for the word 'rather'.
It's a rather obvious thing. > If you think about it it is obvious.
I would rather have the green one. > After some thought I have the
I rather you be there. > I have reasoned you (should) be
there. (since you reasoned it you have made the best possible choice
and that explains the urging undertones of this sentence).
you be there. > (If you ask me,) I would reason that you (should) be
Note that British people often use 'rather' in a deliberate and slightly snobbish fashion. This can be linked to education in ye old days. If you can reason you had an education. If you had an education you had money or was in some other way an important person.
To me it seems perfectly clear that 'rather' has originally been used as a verb for reasoning.
What often happens is that the original meaning gets obscured and a word becomes overspecialized as a particular grammatical construct(s).
Think of these two sentences:
I'd rather be at home.
I'd rather you (would) be at home.
Note that there is a missing 'I' in the first sentence.
Note also that both sentences have a missing 'that'.
The fully written out sentences would be:
I would rather that I would be at home.
I would rather that you would be at home.
Et voila! 'rather' has become a verb!
'would' can be removed as it only signifies a condition, in this case the condition of having thought about it.
It's similar to the use of 'would' in: "I would say..." (If you asked me, I would say).
It's a meta position that came from reasoning (you reason about yourself) and can be left out.
Which makes 'rather' the verb.