How much time it takes for L2 to L1B(company has blanket approval) change of status in US &what is the process??

I am currently outside US & hoping to get L1B stamping done. But due to the recent issues with visa processing systems worldwide, my timelines are getting stretched & I might lose the offer. Hence trying to explore possibility of L2 to L1B (blanket approval) change of status. My employer does not want to wait for 3 months while I get my EAD. Any help is much appreciated!