[Also reposting, from the thread of your other comment...] This problem is already solved in C4 plants, which account for many crops (sugarcane, maize, sorghum

[Also reposting, from the thread of your other comment...] This problem is already solved in C4 plants, which account for many crops (sugarcane, maize, sorghum, barley, etc.). C4 photosynthesis creates an anoxic environment in bundle sheath cells to stop RuBisCO wastefully fixing oxygen instead of CO2. So nitrogenase, suffering as it does from the same oxygen discrimination problem as RuBisCO, will operate efficiently in BS cells. C4 is being introduced to more crops, and that's what I'm working on. So, two birds with the same fistful of stones.