Sounds like a good plan. The Electristar is nice and probably a better value than the Nexstar EP in my opinion. With the Nexstar EP, you'll be paying for wing pods, airbrakes, and an Auto Levelling System that doesn't work.

You'll end up with some additional batteries in the family, but it would be much easier to buy the Electristar RTF than to put together your own electric trainer designed to run the same battery.

Good luck and good shopping!