Just skipping the staircase it not enough. To make the plane taller it needs a new landing gear. But that doesn't fit into the existing gear wells. So now you need to redesign the gear wells. But the gear nearly touch in the middle already. So you neet to make them taller, and attach them to the wing further out. Which the Wing can' take. So you need to redesign the wing. At this point you better just admit that the 737 design from 1964 is at the end of its life.