Everything will be backed up to its own emergency generator so no chance of a failure I would think you could utilise a ground source heat pump in lieu of heaters but this would need a decent control system. This would also be liked to the opening skylight to prevent overheating.
i don’t think evaporation top up would be much different to a normal size tank, water level sensors and a pump from an RO tank.
my lighting would be natural light and overhead supplementary lighting, I would also think I could fix spotlights to the underside of the stairs to provide feature lighting to the bottom.
stocking is interesting as you are going to have to add a massive bioload regularly when setting up or the tank will seem bare, I think a quarantine could easily be set up in the basement along with the filtration, however if I’m going to be buying £100,000 worth of fish I should be able to negotiate that the supplier quarantines and treats the fish in advice.