"add staff" and "remove staff" with instrument changes?

Joshua, the Add Staff/Remove Staff features are orthogonal to the divisi features, which are both orthogonal to the ossia features: although all three features make it possible to change the number of staves used by an instrument at a certain point in the score, they cannot be used together in every imaginable combination. You can’t, for example, use both divisi and instrument changes, because only a section player can use divisi, and section players cannot double. And you cannot use both instrument changes for a solo player and extra staves together, though that particular combination is something that we would not rule out allowing in future if there is sufficient need.