[Sirkit]

They tried something like that in Birth of the Federation, you built a special facility and the effect was either system or empire wide, it worked pretty well unless you accidentally over did it and killed every one in the system and then it was forever lost, this made the minor races verry important because some of the structures bordered on vital to survive, such as research modifiers, the races then had to be treated carefully and the destruction of one was a loss to the entire galaxy.

The minor races had a cool little defensive mecansism, defence platforms, witch acted like really powerful ships that couldn't leave the system, ie. mines, they could make a ship hurt bad by the time it reached the planet and actually got to take over it was sometimes so weak from battle that it was repelled.

There was also something that was important though for certin Empires (ie. federation) bombarding caused revolts, while with say cardasians it 'silenced dissidents' and made the populations happier. But as a balance the feds could negotiate better so often the minor races got pulled into the empire and became 'members', really they became protectorates from the evil romulans oh noooo!