The proposal sounds feasible, but the question is one of economics.  Flares were built for safety from upsets, both large and small.  The idea of using a sphere or tank is feasible for small events, but it will reduce rather than eliminate the need for the flare. Having said that, don't disconnect the flare entirely or it could have nasty consequences. 

Theoretically we can operate plants in balance 100% of the time. That we have flares and the need for them shows that we can approach the 100% figure but not really achieve it. Upsets happen and as long as they happen the safest and most economical control and safety mechanism may be the flare.

Some people find that feeding a flare with steam makes it smokeless and that eliminated the objectionable bright flare and resultant black cloud from the incomplete combustion of fuels.  A typical type of smokeless flare is given here >>  http://www.callidus.com/pages/steam_flare.htm. No endorsement intended.