Fuel saving is not really a thing any more. It was when the new turbo-hybrids were introduced but with the new injection systems and higher efficiency engines as well as increased fuel limits, there hasn't been really a need for running economy for the sake of making it to the end on fuel.
Mercedes engines give more than 50% thermal efficiency now. That is phenomenal.
> Add refueling back, make it more exciting.
Not only is refueling terribly dangerous but I can't really agree that it would be more exciting to see teams play with strategy rather than try to overtake on track or by undercut/overcut on the pit lane (I liked seeing Ferrari play their good old fake pitstop overcut with Räikkönen vs. Perez a few races back, just like in the Schumacher-Todt days).
A lot of people are agreeing that the major inhibitor to the competition are the current front wings. They develop a lot of the cars' downforce and are the reason the cars are so fast at the moment, but completely lose their efficiency when following another car. Compare a last year F1 front wing [0] with one from about 15-20 years ago [1].
All those bits and pieces are there for a reason. They're the product of days and months of CFD work in supercomputer clusters (F1 regulations actually limit the amount of FLOPS in the aero clusters!). Additionally, when there's a minor collision in the first lap, a few of those bits might go missing but not enough to warrant a front wing change. That means that the driver is impaired for the rest of the race, and none if it is conveyed to the viewer (unless Martin Brundle spots it and tells it to the viewers).
A few years back there was the "overtaking working group" (OVG) that looked into this and their verdict was that the rear wings need to be higher and front wings simpler and make the underbody create more downforce (ground effect, without skirts though). Unfortunately that's the opposite of what they've been doing for the past few years and it shows.
[0] https://cdn-8.motorsport.com/static/img/mgl/3600000/3610000/... [1] http://www.racecar-engineering.com/wp-content/uploads/2012/1...