An e-Basket? Where to start?

I've a coworker in the hot-air balloon business who wants to turn one of his baskets (gondola) into an electric vehicle for fairground usages.

He's thinking basket, and three people would weigh 600#. This would not include batteries, motor(s), etc. He wants 15MPH for about 4 hours per day, for 7 days per year. Mostly flat surfaces, with the exception of a slight incline to the parking areas, about 1/8th mile away.

Anyone have any idea what I can tell him?

:)

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