Is it OK to send email to conference chairs asking for resubmission of the manuscript?
I might have a slightly different take than @PsySp in his answer on this issue, but I think fundamentally we agree.

In my view, it's probably fair to email and ask the chair whether you can submit an updated version. But it's also fair for the chair to say no: like @PsySp says, deadlines exist for a reason and you can't assume that you're exempt from them. Get your house in order and build your paper in publishable form before the deadline comes up.