If you race - great! Time is going to be of concern if your competitive. If not, don't bother. Really - you need to carry a pump anyway (I just don't buy it from those who say they ditched their pump - I've had to lend my pump to people who only had CO2 a few times recently)
Just get a decent pump!! I ride with a backpack & love my Lezyne Micro Floor Drive - only 200g Your CO2 cartidges will run at about 50g each and you will need to carry a few, as well as a small pump, so all up probably more weight than my pump. If racing you might gamble on only carrying 1 cartridge.