Dual electric/pedal bikes to solve pedalling effort issues
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.