Some comments:

6 m/s mexes are very fun, but effects player incentive on overdrive. Cutting out the math, it's very efficient to spam many singus, meaning there's a multiplier effect instead of an additive effect when you increase base mex income.

A lot of mexes are not on level ground, which means players need to do something to manually teraform the ground to build mexes. This was a "recent" change to the slope of ground mexes can be built on.

There seems to be no land to water transitions. Hovers and amph bots can't traverse the sheer cliffs at the boundry between land and sea. It would be nice to have some transition ramps, maybe at modern or historical coastal cities.

I've seen you post asking for map making help on the forums. Hopefully someone's pointed you at the wiki, or some other resources. I'm not a map maker my self, so I don't have real advice, but you can ask around on the #zkmap channel on discord perhapse. https://discord.gg/zero-k-278805140708786177 You can do a search like "has: link in: zkmap" and find many links to examples of maps or map making resources over the months.

best i can do is simply keep my mistakes in mind for my next map ideas

The mexes are fixable via lua. Check out the configs under luarules in base game. There should be some examples there somewhere.