applying COS from L1A to H1b 2012

currently i’m In US on L1 visa and applied H1b with consular processing and also got the approval. now i have changed my mind and don’t want to go to india for stamping to avoid the risk, So, can i apply COS now from L1 to H1 to start working on H1b from ocotober first . is it possible? if yes, what is the risk and fee? how long will it take to get the approval on COS. can i go for premium for COS?