As a facilities, RC electric and automotive guy, beyond depleted batteries or really crappy wiring, the "no run" on electric is likely magnitudes better than any gas.
Regardless of FES or pylon.

The electric motor is a ton less, but current battery tech (no pun intended) makes the gas/electric swap (for similar power) a wash. The batteries take a lot of weight, but it's closer to fuselage centerline so the CG effect is limited.

Cost, well, how is it certified and how open is your aviation authority?
Engineering, like marriage, there is give and take, nothing is perfect. Make the best decision you can, live with any potential downside.