Could Holmes pull off a rope a dope in Zaire 1974?

No.

It would not just have been about whether Holmes could take that level of punishment (which is doubtful). Holmes would also have needed to maintain his form under that assault, which is highly doubtful.

And, this is where Ali's greatness is really demonstrated and sets him apart (along with Louis) from the rest.

 

No he couldn't . Here's why. 1st and most importantly is, he didn't have the gift
of gab or personality of Ali. Holmes couldn't create the blind rage Ali was able to
do to opponents.
That rage worked to perfection for Ali in Kinshasha. It made Foreman fight
possibly the dumbest fight in the history of heavyweight championship fights.
Holmes wouldn't be able to get under Foreman's skin the way Ali did.
I would expect and much more calculated, and measured performance
from Foreman against Holmes, he would set up his attack much better,
If Holmes tried the rope a dope , It would end up a disaster for him.
It would nullify his best weapon, his jab.
Ali was very capable of getting his combination punches off in close
quarters. Holmes was more of a long range type, needing more
room to get his offense off. Though as was noted earlier he did use
the rope a dope successfully against Mercer. But Mercer didn't have
the fire power of prime Foreman.

 

No way, Holmes didn't have the experience yet.