I 'm bumping this in the hope that Stardock taks another look.
This is an absolutely huge exploit. As soon as your economy can produce, say, 750BC/turn, you can buy absolutely everything you want for 2000BC. It'll take 3 turns with no production to get out of the red. Big Freaking Deal!
In my last game, I decided to give this a go in the mid game. I was about to go to war, so I decided to upgrade my entire fleet to the latest models of ship. Total cost: 64000. Then I went through my planets and rush-bought Invention Matrixes on every planet. Another 50000. I ended the turn more than 100,000 BC in the hole. But next turn, like magic, I'm back at -2000BC. Two turns later I'm producing again, and the Drengin worlds are falling like dominoes to my upgraded ships.
Now, I appreciate that Stardock wants to keep new players from inadvertently going deep in the hole. But I sometimes play a strategy game called RealLife(tm) that has a good mechanic for this.
In one game, I was playing a recent college graduate. I had $5000 in my checking account, and a credit card with a limit of $2000. I started spending like crazy. Travel. New clothes. New computer. You name it. Pretty soon I had a credit card debt of -$1000. But I decided I really wanted to purchase a BMW and charge another $30000 to my account. See if you can guess what happened? Did the credit card firm
(a) Pay for the BMW, and then credit $29,000 to my account, so I'd be back at my credit limit of -$2000
or
(b) Deny the purchase, on grounds that I had exceeded my credit limit and could not spend any more
Seriously, it should be obvious that (b) is the correct in-game behavior. If a purchase would take the player over their limit, don't allow them to complete it. Credit limits are completely intuitive to anyone who's ever had a credit card. If Stardock wants to add higher credit limits on higher difficulties, that's fine with me. But the current design is a ridiculously large explot.