Actually, with modern electronics, something as simple as a class one EFB- nothing but a Windows lap-top and tailored software- could allow you to optimise feild calculations (including Flex thrust which has a substantial effect on DOC) and even do a good job of calculating optimum levels and speeds.
Add an RNAV approved GPS (Just a panel mounted GARMIN will do) and you have direct-to capability.
Beyond that, I don't see what a G1000 panel would do for you- they are a great interface, but only give the same info analog instruments do in a nice, user freindly fashion, but at a high cost!
If the exersize in purerly DOC without factoring ROI, I guess you might make a case for lower operating costs.
Similarly, FBW improves handling and saftey, but not DOC unless the airframe is designed for it from inception (e.g reduced drag from relaxed stablility) so EVEN disregarding the prohibitive cost, I can't see that helping DOC.