This is definitely top loading, and definitely maintenance/evac stairs.
The ride will obviously safely lower to the ground if powered down etc.
The ride 'well' (at the bottom, where the towers will sit) is slightly bigger than it will be eventually. Once the mechanism is placed in, I would expect them to be made slightly smaller, so that passengers can (if required) disembark from the ground floor.
My imagining of how this will happen is shown here. Red indicates footplates, the blue the theming elements, yellow the drop tower and turquoise some form of 4D effect. Green indicates the safe route should the site need to be evac-ed.