Flexibility for what? Barring a significant injury, Duncan and Ginobili will probably return, in which case Marjanovic replacing West would likely be the extent of alterations to the rotation. Outside of that, the likely 29th pick probably takes the roster spot vacated by West, Bertans replaces Butler and Bonner is probably 50/50.
Though certain match-ups will be an issue, I do see Marjanovic as a rotation player next season and beyond, but as a 15-18 mpg backup. How long he can hold up and how many minutes he can absorb over the long haul, is irrelevant, as he'll probably sign a bridge deal of sorts, along the lines of 2/$10M.