Here's the Suggestion

Economic Treaties- should allow for freer trade between two peoples.

Numbers may need to be adjusted, but this would be much more realistic.

Effects: Vastly is double.
The nation with vastly greater economy:
+10% production as unskilled workers aid production
+50% to trade with that race
+10% of lesser nation's economy as free wealth
+5% to morale for each trade route
Chance of revolt/relations drop due to unskilled workers getting displaced
(depends on political party)

With Equal economy:
+50% to trade
+10% economy
+5% to morale for each trade route due to bilateral trade of luxury goods

With vastly lesser economy:

The nation with the vastly lesser economy:
+50% to trade with that race
+10% of greater nation's economy as free wealth
Factories built 25% quicker (foreign investment)
stronger nations political party gains influence in empire

For research treaties:

Effects:
Research costs are halved for techs one empire has but not other
Research bonus based on tp other empire generates (10%)
Chance to steal techs through espionage vastly increased