As the others have correctly stated your goals will generally be in conflict with each other. The only ways to get better fuel economy ( FE)while not sacrificing acceleration and top speed would be through 1) improving engine efficiency ( difficult, complicated and expensive), 2) reducing rolling resistance ( bearings, tires, chain, brakes) , 3) reducing aerodynamic drag( the biggest mechanical factor ) and 4)using fuel-efficient riding techniques.
1)Advancing the ignition timing may give a small gain in FE at low speeds but would cause detonation and pre-ignition problems at high speeds. Unless you can have easily adjustable engine timing it's a dead end. Running the lowest viscosity synthetic oils that are safe for the moto or any other changes that reduce engine friction would work. Modifying camshft timing and valve spring resistances would work but only at one end of the spectrum.
2) Run high tire pressures, I run mine at maximum rated sidewall pressure. Radial tires would be better if we could get them in our tire sizes. Keep your chain perfectly adjustted and lubed. NOn-O-ring chains supposed offer less resistance. Minimize disk brake drag. Ceramic wheel bearings offer less rolling resistance but are more fragile than conventional wheel bearings.
3) Reducing aerodynamic drag offers you some big gains in FE without reducing sport riding potential. The more complete your streamlining is , the bigger the gain. You would also be limiting your gains if you don't use taller gearing to fully take advantage of the reduced air drag. For your purposes I would suggest an aero windscreen and a removable aerotrunk like I run on my
Silveraero project moto. I average around 90 mpg with it and a best tankfill of 111 mpg. It does have tall gearing ( 15/37 ), but you still would see a significant improvement in FE.
4) Using optimal riding techniques will allow you to get the best FE out of any moto. For the best FE it's all about using every drop of fuel to go as far as is possible. Limit stopping, braking and idling as much as posssible, use moderate acceleration to your target cruising speed and maintain it with the smallest throttle opening, if you see a slow down or stop coming up get off the the throttle and coast as much as possible. Air drag increases with speed by the cube so that if you double your speed you need 8 (2x2x2) times the power to do it. The most efficient crusing speed is 45 to 55 mph.
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Electronic M , what you are after is not impossible , just challenging. Compromise is doable but for me its more satisfying to go all out in one direction or the other. Early on in my riding I loved speed and racing but found I lacked the resource$ and motivation to keep pursuing it. Racing is extremely competitive and already loaded with talented, exceptional riders. I chose a different, less traveled path and have found great success and satisfaction with it. Good luck with your quest and keep us posted with your efforts.