The concept of a “Global Warming Potential” (GWP) of a gas in the Earth’s atmosphere is relevant in calculations only if a known and limited quantity of the gas is being considered.
However, if a constant quantity of the gas, per unit of time is being added to the atmosphere, then it seems to me that a total content stability would soon become established, irrespective of any natural breakdown rate.
Calculations involving the concept of GWP would then seem superfluous. Just an accurate measurement of the actual concentration that become established in the atmosphere and then the specific effect of that gas quantity compared to carbon dioxide seems all one needs to know.