The way they are and divide them in half so that the western side of the current time zone gets the same-ish amount of light as the eastern side of the time zone
Check this out. I'm a business with at least one office in every US state. You want to know when my New York office opens so you can come by. Instead of seeing "Offices are open 9 AM to 5 PM" You now need to check every office... by state.. by city? Time zones would be helpful even if we all used GMT, so that you could easily determine which time zone a business is in to set a reasonable time to be open.
Typically people propose switching everything to UTC.
The read this doesn't work is because humans are still bound by a diurnal cycle and you won't have everyone wake up at 0800, since for some people that's the time in the middle of when the sun sets and rises.
So you still need to communicate to people across space where the sun is or will be for you at a time in the future, or otherwise relate where in your wake cycle you'll be.
Tied to this is legal jurisdictions. Within a legal jurisdiction it's important for regulatory events to be synchronized. For things like bank hours, school hours, government office hours, things like "no loud noises when people tend to be sleeping", "teenagers old enough to have a job aren't allowed to work late on school nights", and what specifically constitutes "after hours or weekend labor" for the purposes of overtime and labor regulation you need your definition to be consistent across the jurisdiction. Depending on where you are in relation to Greenwich a typical workday can start at 1900 Friday night/morning, and extend until 0300 Saturday morning/afternoon. Your "weekend" would start when you woke up around 1800 Saturday evening/morning.
Right now we solve this problem by deciding on a consistent set of numbers for where the sun is across some area that inevitably lines up with legal jurisdiction. Then we use a lookup table to translate our conception of where the sun is to where it is elsewhere.
Without timezones you instead need to use the same type of lookup table to find the position of the sun at the time and place of interest, and then try to infer what the situation would be.
We have UTC now, and people inevitably already use it where it makes sense. It's just usually easier to have many clocks that follow similar rules than it is to have one clock that's interpreted many different ways.
As a British person I agree with your second point. Everyone should use Greenwich Mean Time which is obviously the correct time. Even if it means that noon is in the middle of the night for some people.
I want the most anti-British option. I know! We're going to do away with clocks entirely. We wake up when we wake up. We work when we work. We forget counting the days. Forget the calendar entirely. Live forever in an eternal now.