Man, I was in this SAME EXACT situation a few weeks ago about storing a bike in a basement with the hactchway and the steep ass steps.
I never got into it because the basement itself wasnt big enough to maneuver around. But the steps did have me worried cuz it was so steep. think I could have sent plywood down into it, but the it looked like inorder to get plywood long enough to lessen the steepness, then the bike would ride 'too tall' and would scrap the ceiling on entry. Or not make it in there at all. So good luck with it. I know how its gonna be...