It does, as they say, take two to "tango" but the granting of any aircraft handling by the Captain is a privilege and not a right!
That said, notwithstanding different airline policies, a good Captain will grant handling to the F/O so that the latter can keep in flying practice and also be coached for the job of Captain.
However it is my view that the F/O must be able to do the non-flying role satisfactorily before being able to conduct a sector him/herself.
If I am flying with a new F/O (especially with low hours), I want to assess his capability BEFORE allowing him/her to fly a sector. This means that I am not going to decide when and if he/she will fly a sector until the time is right!
If you want to upset your Captain from the word "go" then ask him early on which sector you are going to fly! This question presumes that you will be allowed any handling at all. Remember the Captain has overall responsibility for the flight and he/she will have safety as a prime consideration.
Regarding fuel, well it's fine for the F/O to get in early and think about what he/she would take but it is NOT his/her decision.
As a training captain years ago I checked in for a flight to Madeira (Cat C airport, short runway, then) and the bright eyed bushy tailed F/O (ex Harriers) had discovered we could tanker fuel and had calculated the fuel to land at Max Landing Weight - he had not given the performance considerations any real thought. I bit my tongue and quietly acquainted him with the facts! If I had gone in with "guns blazing" it would have set the wrong tone from the start of the working day and dampened his enthusiasm for the job.
However, I do think these types of issue point to lack of comprehensive line training.