You create an access under the stairs in a wall if this is going to be a finished area. You have to be able to get TO the basement .........and you are doing what? Relocating a stair to a new location ? The pump is inaccessible in its current location? If your remodel includes burying a sump pump somewhere inconvenient to access ? Bad idea. Not to mention the sump pump should be equipped with an alarm.

I don't understand a removable stair. ......or why.If the lowest level gets water in heavy rain and is prone to that? You need more than the sump pump. ..........meaning an outside the house solution in gutter extension, french drain.....etc. And don't forget the alarm on the pump.

I need to see why the stairs need to be removeable since if there are stairs there is a space under them that is accessible . I agree if this is a common need then you need to address the waterproofing and control from outside too. The alarm is awesome and a great idea. You need to post pics and I do not think removeable stairs could possibly be the answer.

Do you mean removable as in temporary till you get the permemant stairs.. or removeable as in you plan on having no access unless you put the stairs in place? Where would you store the stairs when not in use? If your basement is flooding, you might not want to be taking time to set up removeable stairs to gain access to the pump. You would have to check, but not having permenant stairs might be a code violation and/or impact future resale.