DrJamesWhite... sorry for being presumptuous, but heck, let's be informal here, may I call you James?... you keep on saying nobody has given you an explanation on why CO doesn't allow for a setting to expand to whatever size people want based on what they have the capacity to run.
Truthfully, I have found various explanations for that in these forums already, including on this thread. But all of that aside... let me give you one possible explanation that aligns with exactly what CO has been saying. If I were in charge of CO (dream job!), here's how I would be looking at it. Even if I knew this were conceivably possible, what happens if I add all the optional sliders in the world? 25 tiles, heck let's go 36 or 49 just to be daring. 1m? That's NOTHING... I've lived in Cairo... I say 10m is my bare minimum. Now, we put the option sliders in there, we could put all the warnings in the world about minimum system power, but what happens when the game gets released? No matter how many warnings you put up, reviewers are always going to comment on the fact that there's serious lag if you push toward the upper limits... another reviewer might say "the end game really suffers under the pressure on system resources, even with a good rig". The devs cannot afford that type of review. How much better this review, "The game allows you to create a solid mid-size city, on a really decent plot of land, and it functions really well with minimal lag." If I were Mariina, THAT'S the review I'd be shooting for.
Even with their recent announcement on providing a bit more latitude for people to tinker with the 25 tile issue, their warning was super-clear: they take no responsibility for doing so. They want everyone to evaluate their game as a function of how well it performs at the size they feel optimizes performance. Any action they would take to "open it up more", no matter how much they caution people against doing so, would be conveniently forgotten the day it gets released. The game has to be functional at whatever size they officially allow.
And to be honest, I was really disappointed about this originally myself. I wasn't convinced about the need for the agent system, and I would love my 10 million city, cause that's what I used to live in. But the more I've read about what becomes possible with an agent-based approach, the more I have been won over to the opinion that this is a solid trade-off.
So, I don't expect to convince you of anything, based on how strongly I can see you hold your opinion, but pls don't imply that there's no possible reason under the sun for CO to take this approach. Their approach is highly logical (nod to Leonard Nimoy, RIP), and most of us accept those reasons happily and are ready to move on.