Ditto on the batteries. I have a Twin Otter with Power 25 motors, and 8000 mah 3S packs. That gives me 10 minutes of flight for 90 minutes of charge time. The 2 packs costs me over $200. I have 5 3000 mah 3s packs, they give me enough power to take off, fly 4 patterns and land, and that is about it. I started out flying electric with a T-34 Eflite, and an Apprentice, then built my LT-40 with an OS-52 and never considered electric again. The Twin Otter was given to me already built, and would take some major work to convert to fuel. I do have two new Nacelles and Cowls for it if I wanted to, but would be a PITA to remove the existing ones. The plane isn't interesting enough for me to want to spend the time needed to convert to fuel.
I checked into electric motor and controller and it would be close to $800 for them, plus another $300 or more for two 12s batteries to give enough flight time. I would get one flight and then wait 3-4 hours for the batteries to recharge. I can put that Saito R3 on for what it would cost for the motor, controller and 2 batteries.
Since I already have the DA 100, and the servos, and everything else needed, I wouldn't even think about changing at this point.