Hmm, perhaps it would work for LINQ to objects, where the LINQ statement just becomes a delegate that is executed at runtime. I can't see how it would work for LINQ to anything else (SQL etc..), where the compiler only emits an Expression which is then consumed to generate SQL/Amazon queries/whatever.

Can always write your own query provider :)

Yes, but someone needs to create an expression out of the LINQ statement, so that the query provider can do its job.

I suppose it is possible to build expressions with just libraries, but that would be very ugly (like control flow in XML) :)