Dual electric/pedal bikes to solve pedalling effort issues I prefer the good old pedal bike. For obvious reasons, I cannot get to the office sweating, and I have no time to shower before I get into the office.
I have no issues biking uphill and steep road segments. However, the electric bike has changed all of that. In addition, the bike seat had to be lowered to suit my height, and pedalling when the knees are bent too much is not a great idea.

Details of the problem: My bike has a rear-wheel built-in electric motor. It cannot be connected or disconnected. I can either turn the system on or off. However, that does not solve the problem. In my experience, pedalling with an electric bike is much harder than with a regular bike. I can pedal a bike uphill with a reasonable speed. However, an electric bike is even hard to start pedalling from zero, and even maintaining the same speed as the motor is not longer than a minute. After some time, I had to walk and pull the bike. My bike has a gearbox, but that means I can walk faster than pedalling. In comparison, I can achieve a slightly higher speed with a regular bike, so fitness is not the issue.

What I tried to do: I tried to check the gears for too much friction, but the wheel turns fine and slows down reasonably when I stop pedalling/throttling. I tried to see if my extra effort can be used to charge back the battery, but it took much effort for too long, and I think it didn't work because the throttle was off. In addition, I don't know if it makes much difference because the battery takes few hours to charge.

Any solutions?


Would I use a throttle to allow charging back by pedalling or going downhill? (Regenerative braking, not perpetual motion machine).
replacing the battery with a capacitor to improve efficiency of regenerative braking? The idea is to do biking sport, but storing excess energy for commuting to the office without pedalling and sweating. 
Any e-bikes with an outboard engine which can be engaged/disengaged to the wheel?
Not sure if I understand your question correctly, but I take it you want to ride unassisted during training/recreational rides?

I don’t have much experience with electric bicycles but as far as I’m aware the motor often has its own free-wheel and therefore should contribute very little friction/resistance when it’s not running. The disadvantage of such a free-wheel equipped motor is that regenerative braking is not possible. So if you remove the battery the only major disadvantage of an electric bike should be the mass/weight of the motor and charging controller. With front wheel drive it should even be possible to swap the whole front wheel+motor for a normal wheel relatively quickly.

Of course many electric bikes come with “comfortable” seating positions, heavy frames and other heavy parts. This doesn’t help when you want to ride unassisted.

Regarding 


  the bike seat had to be lowered to suit my short stature, so that I
  can put my feet on the ground when I stop.


It shouldn’t be necessary to reach the ground while sitting on the saddle. Get in front of the saddle just before you stop and you should be able to reach the ground just fine. There is only one requirement for saddle position: It should allow you to ride powerful/efficiently (and without damaging your body). You should never lower it to reach the ground or move it front/back to compensate a long/short top tube.