It may not be completely impossible, but even with the DLL source code that would be a huge project, almost everything in the game is coded based on cities. And now that Firaxis doesn't plan to release the gameplay source code for civ6, that's a project more fitted for civ5 or civ4 modding. Or as the base design of a new game.
There are a lot of good ideas in the Ideas & Suggestions forum, but a lot of them are difficult to apply in a mod (especially with civ6 limitations), for a quick example the simple action of "work[ing] a tile with 3 food or more" (without a city) requires a lot more of code that one may think. Code for the new action in the interface (that also has to be designed for tiles), code to share the action to other players in MP, code so the AI to know how to use it.
For example in my overhaul, yes, there is population on tiles, with migration and push/pull effects, one being food, but something I tried to do from the start is to have the new mechanisms to be linked with the possible actions already coded in the game (for example working a plot from a city, an existing action, affect migration on that plot, my mod new mechanism), it saved a lot of development time. Still, with 3 years of development it's ~50% done before being feature complete and called an "alpha" version.
Now about "we", one thing I've realized in the forum, is that generally "we" all agree that something would be better if it was overhauled (population growth), but when it comes to details, you'll get almost as many different ideas that there are people behind the initial "we".
Not that it should prevent you from proposing them, Ideas & Suggestions is my favorite forum on CFC, but you must be aware that for the realization of those ideas, if you want it done right you'll have to do it yourself (or be ready to see it changed a lot in the process).