I feel like this suggestion doesn't quite fit the bill of adding a new government, but also doesn't exactly fit into tweaking existing governments, thus I'm putting this suggestion in its own topic.

This suggestion, Enhanced Governments, introduces additional benefits and drawbacks beyond the base adjustments to the existing government types.

Enhancing your government has 2 prerequisites and a cost:

20,000 Acres
$5,000,000 Net Worth
Pay 20,000,000

Once you have enhanced your government, you can not change governments for the rest of the game unless you die. Adjusted benefits for enhnaced governments are as follows:

Monarchy
+5% Food Production
-3% Expenses
+1% Maximum Technology

Fascism
+25% Food Production
+60% Oil Production
-10% PCI
-10% Max Population

Tyranny
+30% Attack Gains
-15% Military Upkeep Costs
-10% Max PCI
1 Turn per attack

Dictatorship
+30% Military Strength
+35% Spy Effectiveness
+50% Ghost Acres
-20% Construction Speed

Communism
+20% Technology Effectiveness
+5% Maximum Technology
+40% Industrial Production
+45% Market Size Sale Cap
8% Market Commissions

Theocracy
-30% Private Military Costs
+50% Construction Speed
-20% Maximum Technology
+60% Maximum Population
1.5x GDI Expenses

Republic
+50% Exploration Rate (After all, you need 20k acres to upgrade)
+30% Max PCI
-5% Military Strength

Democracy
0% Market Commissions
-25% To-Market times
+10% Maximum Technology
(2 turns per attack)

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Revised to lessen the blow of the drawbacks. Makes more sense for "Enhanced" government.