CO2 and O2 concentrations are completely independent of one another on a fundamental level. However, in your typical planted tank, O2 levels are below their equilibrium levels and CO2 levels are above their equilibrium levels. Therefor, increased gas exchange negatively effects CO2 and positively effects O2. In a system like a river, the constantly moving water breaks up surface tension (and therefor has higher gas exchange), giving both CO2 and O2 a higher dynamic equilibrium than in slower or stagnant water.
However, if you were to set up some sort of O2 injection system, you could maintain both O2 and CO2 levels above their equilibrium concentrations. Otherwise, your best bet is to have to gnarly surface disruption. My thought would be two powerheads, both pointing clockwise, on opposite sides of a tank.
Dunno if anything would want to live in that whirlpool though.