No problem either - do it like on freefall towers or on other park attractions, where eddy current brakes, fully passive, are employed as safety mechanism.
All elevators have multiple safety brakes working on their guide rails (this is the famous invention of Otis); so do these. Besides batteries lasting longer (two hours, they say) than the median European power outage.
Plus hopefully battery banks (which you'll likely want on the elevators anyway to be able to store energy from regenerative braking) to power the car long enough to come to a rest where the passengers can get out in the event of a power outage.
There's going to be several layers of safeguards, like there are with current elevators.
