seems a bit silly to me with the cost diffrence.
a 20oz CO2 botlle is about 40 quid and 1.1 air bottle goes for around the 150 mark brand new. so don't see much point in it unless you want to waste money.
plus a CO2 bottle only pressures to around the 850-900 psi where your air bottle is tested to 3000 or 5000 psi. also you don't know what effect the CO2 will have on the inside of the bottle.
sorry to me seems a pointless excirse.
just my thoughts