You know there's an entire strategy to nuclear warfare? And nukes aren't an easy button at all, not with those with war chests. More than likely, in an alliance nuclear war, you'll still be doing conventional attacks, just money management becomes 10 times more important.
Regarding the wonders, the SDI is overpowered. It should either decrease the damage of the nukes or be only effective in stopping around 20-30 percent of the nukes, not 60 percent.