Signing a QO FA SP and trading significant assets for another is a lot of player capital used when you do have decent depth. Assad, Wicks, Brown, Wesneski, Horton, Birdsell as options 5-10 is not a problem, especially if you fortify the pen that you don't have to use those folks there outside of long relief if desired.
There's 2 situations where I could see them adding 2 SP. One is if Sasaki is posted and they win the race for him, since he's functionally free in both player and financial terms. The other is if they like a SP and he carries a similar cost as one of the RP they would be adding anyway. Beefing the rotation and leaning on Brown and Wesneski in particular out of the pen as needed is fine, it's just not very certain you can find that SP target/RP target equivalency.