The staircase remodeling is going slowly, at a rate of two days of thinking for every two minutes of actual work, but the thinking is beginning to pay off. I'm starting with the second floor run, which is straight. This is what it looks like using kit parts.
Looking at the backside, the new bits are staged. As you can see, I've started staining the new parts. I finally figured out that the stain is Provincial by Minwax.
Not shown, the delicate procedure needed to detach the flat bannister/rail piece from the staircase unit. The thinking part included a debate between salvaging the lower part and making an entire new surface. The salvage idea won. Using a combo of sharp utility knife, mini saw, and emery board, the demolition began. I cut it away to line up with the risers and the underside of the steps. This, however, left a disturbing void between the edge of the step and the outside plane of the facing, which triggered more thinking.
The result of the thinking calls for a piece of strip wood to extend the step a bit beyond the facing. It will be rounded to a bullnose silhouette and stained to match the rest of the unit. The facing has not been glued yet. It may need some gentle sanding on one or more steps to fit the strip wood snugly enough so as not to be very noticeable. The stripwood has been ordered.
Meanwhile, the thinking has shifted to the railings that edge the opening between the first and second floors. I think the balusters for the upper run of the ground floor unit will actually be attached to the 2nd floor railings and simply hang down, so they, too, can be removable. Need to make a mockup to test the theory.