Possible thread creep, but relevant I hope:
On the Airbus, the only time the speed control part of the FMA is blank is when the autothrust is completely off - i.e., not active or armed. At all other times, it gives the status of the Autothrust; either Speed/Mach or Thrust Climb or Thrust Idle or MAN FLEX, TOGA etc.
I don't know Boeing but on the ? 777 PFD shown in this thread; during FLCH mode, the Autothrust 'speed' annunciation seemed to move over to the pitch box leaving the top left speed control box blank.
So I wonder is there a danger that since 777 pilots get used to seeing a blank box top left when the Autothrust is still operating, this might lead to some missing the clues when the Autothrust is actually off for real?
(For example we have seen from the SFO 777 crash that non movement of normally moving thrust levers is not necessarily a clue that the autothrust is not controlling speed?)
Could this be why the sort of additions proposed by the OP might be thought necessary?
(NB: I have not flown Boeing, but this is not an A vs B bashing at all, I am merely trying to understand the psychology and causes of some accidents).