This is a very interesting question. You're right about being introduced to the lead character first and identifying with her, because we learn more about her for longer...but I wonder if any drama could logistically advertise a story where the secondary gets the guy...it would almost seem like the secondary girl becomes the lead somewhere along the line.
But, if they established that she was the secondary from the beginning, like the format in Style, then perhaps it would work for more dramas. If it was due to star power, they could hire the more popular actress as the secondary, but then, would people see it in the same light they see her as a lead female?
I would be interested to see this implemented more in the future :)