Actually, we wouldn't have to change it to total changes. I think if we only changed how production changes is computed that would be enough.
Changes on production are displayed as zero when there is a standard production. That's the reason why zero production is displayed as negative production. If we change the zero production to display as zero, than the standard production will be displayed as positive production.
Example how it effects changes
Current:
Normal: 0/0/0
Quick: -3/-3/-3
After this change:
Normal: +3/+3/+3
Quick: 0/0/0
This should fix this problem, however the cost is really high.
Different approach would be to implement a limit one the card (anomaly sphere) so it wouldn't give resources to opponent (apply only negative changes).
EDIT: I would prefer to change the anomaly sphere ("Negates the effect of opponent's last round on his tower, wall, facilities and stock") effect to something like this:
"Negates the positive effect of opponent's last round on his tower, wall, facilities and stock"