The cable/belt mechanism of elevators has remained largely unchanged for most of it's history because of its simplicity in design, manufacturing, and maintenance. This new system is absolutely beautiful, but I agree, it looks expensive. Elevators have to work 24/7 with little maintenance, it will be very interesting to see this in the real world.

If the rails are solid state using for example magnetic levitation, I can see this being much cheaper to maintain.

Ever been in an elevator during a power outage?

Probably no one at ThyssenKrupp thought of that. You should write them a letter outlining your concerns.

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.