Or so i thought
As soon as i reached chapter 3 (after promotion to Commander) i got one of my planets warning me an invasion was coming to them.
From there 2 choices as there's no planetary defense yet and no money to even try to build them :
1 - i wait for the enemy fleet to arrive, drop all their tanks and try to beat them on the planetary surface with my own tanks.
2 - i use my fleet and go to intercept and destroy the enemy fleet before they arrive.
I choose 1- , i see that they have 2 times my amount of tanks, and have not like me only light tanks, but medium tanks and artillery too, basically game over.
Reloading i choose 2- , see the screenshot on my previous post ? That's exactly what i see, so no more fleet and the whole system is undefended now.
Scratching my head to understand if OpenIG had simply utterly destroyed the campaign balance or if i did something very wrong (despite it didn't seemed to as i was following missions and objectives), googling a bit taught me that the error was mine.
I learned that in fact i had completely screwed up my campaign right from chapter 1 (as in further chapters you'll keep playing the same system of planets, the area will just expand with new planets and enemies) , by trying to complete each objective as soon as they appeared to complete a chapter fast.
But that's the best way to destroy any chance of surviving in the campaign later.
Playing the way i have played had me in chapter 3 generating roughly 8000 credits a day (even at max speed it still takes time to have a full day completing) and that's ridiculously low at that point of the game as at chapter 3 you really need to build tons of very expansive stuff.
So starting from chapter 1 it's -very- important to build enough morale-increasing buildings on each worlds to afford to set the taxes on every planets to their absolute maximum.
That will make a gigantic difference in term of daily income (so much that when i restarted the campaign, near the end of chapter 2 i am at + 48000 credits daily in comparison to my 8000 by day in chapter 3 of my first attempt it's really night and day) .
After that for some minor (in comparison with taxes money) more money , you can build trader ports and their banks if you want, as you'll swim in money you'll be able to build a lot anyways.
Basically : don't ignore the mission and objective (as the HQ willl fire you on the single objective failure like one of those numerous "save a trader" mission) , but make sure to build from the very start of the game the best economy with setting the highest taxes you can, counterbalanced by morale+ buildings.