I’ve heard from many people who think that this isn’t possible. That once you pull an app from the store you must essentially abandon it. That is simply not true.
So long as you don’t actually delete the old version of the app within iTunes Connect you can continue submitting updates to apps even while they are in the Developer Removed from Sale state. Whether this is intentional functionality is unclear but I have verified that it does in fact work and the resulting approved updates are available for customers.
Interesting. I assume that "available for customers" means the update won’t be pushed to their devices and they have to use the purchases list to download it “again,” but that’s still better than nothing.