I am curious about it too, but in this way, you will need prepare all your doc again, it will cost a lot . like new IELTS result, criminal clearance certification . birth , Id certification. .etc , anyway, I don't think it is a very good idea. except you have found some very possible mistake in your CEC application.
and express entry also take 6 month at least , not guarantee 6 months, current CEC average time is 13m, but check history, usually 6-7 months the reject or accept result would have been finalized.