If I understand you correctly, You are going to remove the door at the bottom of the stairs.
How are you going to access the cellar?
Are you aware that if the only access is from the outside world, you may be creating a dwelling unit!
Do you have enough room to have an egress in every bedroom to the outside world? (Not a 32" X 16" cellar window) 5.7 square feet of clear opening? If you you not have the availability to install the egress windows, (because they would be under ground), you may be able to install a domestic sprinkler system instead (often, no more than 6 heads).
Remember a hard wired smoke detector in every bedroom
I would strongly urge you get your Building permits!
If disaster strike, your insurance company will pay out alot faster if you do.
If I have miss-read your post, I apologize!
As you can probably tell by now, I have a real problem with bedrooms in the basement.