Thinking out loud: GBs (at least some of them) used to be the best buildings you could have -- the only way to get extra troops (Traz), fighting boosts (CdM, CoA, Zeus), goods, population, and happiness (etc). Earning FPs was critical to leveling GBs and with the Arc, 1.9+ threads worn born. Sooo many newer buildings are better than almost every GB, how do you make them great again? Obviously, you must make them produce much more across a wider spectrum. The GB buff will in turn add to the power creep which made the GBs mostly obsolete. In order to combat this power creep, a large scale leveling across GE, GbG and QI would be required i.e. make all three much more difficult to offset the GB buffs. Additionally, new special buildings should be equivalent or marginally better than previous special buildings so as not to reduce the worth of GBs again and slow the current power creep. Such a vicious cycle.