From what you've said, and you seem concerned about safety, I would say yes, you could, though if you're using all those new circuits while you're waiting, you risk a brown out, or tripping your main breakers.  While you're replacing the box, you may as well replace the wires from the meter to the box with a thicker gauge appropriate to 200 amp service, and upgrade your ground to modern standards.  This of course supposes that your 100 amp breakers will fit the 200 amp breaker slot.

The real question I have is, why would you want to?  How long after you install the box will it take to upgrade your service with the utility company?  The ones I've done, the utility company comes out within days after the inspector passes the work.  If your work isn't inspected through a home owner's permit (if those exist in your area), you're taking some risks.  Some with safety, but some with your insurance.  In case of a fire of any kind your insurance company will inspect your wires and deny your claim for non-permitted or non-inspected work.