This thread covers the answer for players who may be usable as both position players and pitchers.
Before Otani, there was Bethancourt. The proposal in that thread is what is implemented on the site - pick either pitching or hitting on a given day/week for players who both pitch and hit.
He will be treated like any other player with multiple earned position eligibilities - no different from a 1B/OF. SP won’t come and go depending on the day or anything.