Chris,
(1) It should NEVER be made by the pilot who performed the selection. If the other pilot fails to make the call, making it yourself is valueless at best. This is not a competition, nor a box-ticking exercise. Wait for your colleague to come back into the loop. If necessary, any prompting should be on the lines of "Check your FMAs?" If his/her workload is too high, best leave it be.
Our SOP is that the PF calls the FMA change, the intention ensures that the PF communicates their actions. This I bought into. However, I'm thinking it would make more sense the way you describe.
Thread contributor Check Airman doesn't see the point of calling out expected FMA changes, which I kind of agree with, yet I still think it would be wrong to not actively recognize such changes. With your philosophy, if the PM is required to male the call, then the PF is also armed with strong cues alerting him to possible PM is overload/distraction. Works for me.
Just edited to add that PM/PF in this case is assumed with A/P engaged.