As far as pure population count goes, that is where the Size 12 Plan(which everyone seems to love, according to the polls) comes in. Maybe I am trying to do too much at once, but we have the tools right now to improve our situation almost overnight.
I am currently offering all these ideas because they are meant to work in tandem.
Democracy would help the Size 12 cities(with emphasis on commerce-heavy harbor towns) grow our treasury to the point we could raise the science rate, which will allow us to once again become competitive in the tech race.
Democracy increases the efficiency of our workers to build rails to other civs. faster, to build fortresses faster, to put much-needed mines in hills faster so our cities can build units and improvements faster.
Democracy lowers corruption across the board to allow our far-reaching cities to build units faster, improvements faster, and add more money to the treasury than they can right now. Those cities and any others we conquer will be practically useless without Democracy.
Democracy will enjoy a smooth transition due to eight luxuries we have....all eight! With an emphasis on markets and a Domestic Leader that pledges to keep an eye it, war weariness will be kept well in check.
All we have to do is endure 4-6 turns of anarchy and then watch Fanatika grow:
-Watch Fanatika get to Panzers before anyone has tanks.
-Watch Fanatika build and expansive rail network in no time flat.
-Watch Fanatika's treasury grow to the point where we could consider rushing factories.
-Watch Fanatika react confidently to any threat becuase it has the production and treasury to back it up.
War is possible under Democracy, folks. We have the tools in place to benefit from it and kick butt at the same time. I will consider this term a personal disappointment if I am not allowed the opportunity to prove that to you.