The conversion isn't a problem since the Twist is effectively just a good alloy utility bike.
However, you can't take the Panasonic motor unit off and sell it, as it incorporates the entire bottom bracket with cranks etc. What you can do is strip out all the unnecessary gears, electrics and pedelec parts, leaving just the pedal crankshaft in place with the chainwheel, taking around 2.5 kilos off the weight. The light electric motor it uses can also be taken off, but a blanking plate would need to be made as a cover for the crankcase.
You'd also have a big gap where the Giant battery normally sits, as the BionX battery couldn't be fitted into that space.
Personally I think a normal 24 volt hub motor would be a better choice, since that could use the existing battery, and that battery can be recelled repeatedly and used for ever.
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