I have figured out a work around for the maximum goo accumulated before going minus. This will be added in an upcoming update. The goo will be displayed like '163.3 (Billion) Goo' for now. If people start exceeding this limit, it may be extended to a much larger number.
I don't see why people make suggestions for this game as the developers haven't updated in a while and probably won't update any time soon. The developers are working on the IOS version of ninja warz and probably other games too. If people wanted to make this game better, you could have a chance at trying to apply for their company and sending ideas directly to them, or simple just create a new game just like this one but with a different theme (E.G. Pirate Warz or Monster Warz).