This would be a great way to extend a campaign if you could - for example - generate a "Deathworld" zone of every planet in addition to a standard one.

The concept is interesting, but as it stands I don't actually have a use for a second (or third etc) Gleba clone - but one generated with maxed out pentapods and far larger fertile patches would create a great reason to go through the trouble of building it all again.

That's certainly possible. I acknowledge that this mod is just a proof of concept in its current state. I have two ideas for how to differentiate the different planet zones.

Equatorial Zone: This uses the planet's default settings.
Temperate Zone: Increase resource density, but start evolution factor at 80%. Solar power reduced by 50%.
Polar Zone: Change the day length to be equivalent to the planet's year length, to reflect the long day and long night pattern of polar regions. Nauvis will have a year length of 365 Nauvis days, and the other planets will have a year length calculated relative to Nauvis with Kepler's Third Law. For Nauvis, this means a year will be around 42 hours long. Solar power reduced by 75%.

Looking at the modding API, there is a way to control solar multiplier in control.lua. This opens up the possibility of changing solar output based on the time of year in temperate zones.

Super, I'll keep an eye on what you come up with!

I'll just add a +1 for differentiating zones by difficulty - scaling from a "peaceful" base planet, to deathzone.

Starting off relatively peaceful, then ramping up the biter/enemy difficulty (when I choose to) is my ideal playthrough, this would be perfect.