So if said controller has a medical episode?
I'm going to pretend to know exactly what would happen in that precise scenario but I'm confident most commercial pilots get enough training to be able to handle it.
You are defeating your own argument :-) Its exactly because every accident is an example of multiple things going wrong at the same time...that you need...multiple layers of control and safety to catch it through each hole of the cheese.
Like...another controller?
You need to recognize when something is out of the ordinary and treat it as an emergency (perhaps not a literal pan-pan/mayday emergency) sooner rather than later, and do things that may end up to have been unnecessary (like executing a go-around because emergency vehicles were on the move).
One controller on two frequencies is another example - that works fine in normal situations, but during an emergency response, perhaps the channels should be mixed; giving the pilots in the air a chance to hear the incorrect clearance onto their runway.
After all, an active runway is really more of an "air" control thing than a ground one.
“If we remove regulation and safety controls, things will be safer because everyone will be more careful.”
Because the parties involved would be more careful if there were no ATC?
In practice? It depends. Delays have a tendency to cascade in the air travel system and the Port Authority can curtail or cancel the curfew at their discretion. How frequently do exceptions to normal ops have to happen for it to be unreasonable to use "normal ops traffic" as a justification for scheduling a single controller? Ultimately, controllers have to control the traffic that they get, not the traffic that they want/expect to get, and a system that is overly optimized becomes brittle and unable to deal with exceptions to the norm.
Ever?
I think the better question is how you get a system in which people are only responsible for any one facet to get the same performance out of people that a painter can get out of himself when he's setting up his own ladder that he personally has to climb on.
Mandatory scaffolding for roofing contractors would save some amount of deaths/injuries (and the related expenses) but add expenses to each job.
Some roofing firms refuse to operate without scaffolding; you pay for it or you find someone else.
A painter who does a bad job setting up a ladder is going to have a bad time, a lone ATC operator having a heart attack potentially puts multiple large aircraft full of people in danger...
How many fatal accidents are reasonable in your opinion?
Do you really think it's appropriate to have zero margin for handling unusually high ATC workloads? Because we just saw what happens when you have zero margin for handling unusually high ATC workloads: people start dying.