I wonder whether it'd be possible to augment the CO2 with something that would make it more detectable visually and aromatically, like we do natural gas.

Natural gas is naturally odorless and colorless. Therefore, by default, it can accumulate to dangerous levels without anyone noticing until too late. We make natural gas safer by making stink, and we make it stink by adding trace amounts of "odorizers" like thiophane to it.

I wonder whether we could do something similar for CO2 working fluid this facility uses --- make it visible and/or "smell-able" so that if a leak does happen, it's easier to react immediately and before the threshold of suffocation is reached. Odorizers are also dirt cheap. Natural gas industry goes through tons of the stuff.