After a few more playthroughs I found a way to have fun with a high difficulty level – challenging, but not too hard and not too grindy.

Coz I could not adapt the code, I played with a “house-rule”.

The principle is: the more developed the society of the isle is, the more luxury the colonists will demand, beside sleeping rooms. They want additional living rooms, hobby rooms and whatever.

So I assumed, that 21 ppl will demand 50 rooms in a progressive way:
Colonists: … … … 8 - 9 - 10 – 11 – 12 – 13 – 14 – 15 – 16 - 17 - 18 - 19 - 20
Room demand: . 8 - 10 - 12 - 14 - 16 - 18 - 20 - 25 - 30 - 35 - 40 - 45 - 50
Exception: e.g. if you have 15 ppl and 25 rooms, and you get a 16th colonist as a bonus, you may keep it. But before you can order a 17th one, you should prepare another 10 rooms before that (25+5+5 = 35).

Since I have some experience with this game, it was easy to medium for me, but others might find it challenging – hopefully.

I also tried the sequence for room demand once:
8 – 10 – 15 – 20 – 25 - … - 45 - 50 (18 ppl max)

But stopped it in the middle, not coz it was impossible to play, but it would have taken too much time to finish, and I felt this being to grindy in midgame.

There are about 20 different jobs in the game, so with 20 colonists, it should be a fair try.

Game takes a bit longer (longer fun!), but the main reason to play like this is:
You need more strategical and tactical thinking, more organization and management skills. You really need to have the right person (with special skill) on the right place in the right time, specially if you want to get the most bonuses for finishing tasks withing the time limit.

And to leave working places empty temporarily and gather lots of ppl on other places. To sell something or to keep it for a while.

Avoid to run out of stuff with essential goods, like food, wood, stones, forge products, as well as goods for building in general. Being out of food is worst case, coz then ppl will refuse to work, even in the kitchen and on the field. They just refuse to follow any of your commands.

That’s not a “game over”, but I felt it as a fault from my side (bad management). So I preferred to start over and have a clean PT.