It is interesting to me that the OP starts out with the 1/4 ball fractional technique and progresses to 1/8th ball fractional. Good progression. It is also good because it breaks the game down. I memorized(muscle) 4 then move to 8, ok. . .
Then I would throw onto that what other's have said about having to refine it further to be effective on larger tables and smaller pockets.
Ghost ball is ok, but it doesn't have a simple learn it effectively in a day point like 1/4 fractions.
I would say my knife slice method is really advanced fractional. That is there are an infinate number of knife slices which can be made. Just like fractional, you imagine where the edge of the cue slices the object ball.
Frankly from a teaching and wanting to teach stand point, I would want 1 hr modules with 8hr practice between modules.
Simple - full ball
Basic - 1/4 fractions
Intermediate - 1/8 th
Advanced modules -
1/8th fractional + fine adjust (like Unertal scope use in Marine corp - yardage +/- ?3 MOA of fine tuning available)
instinctive muscle memory aiming(relies heavily on your approach and centering down in your stance)
throw effects
aiming jacked up
etc.
So, now I will address the Efren reference. I believe Efren to be the best player in the world.(my opinion only, no flame war will change it.) . . .BUT, I believe by the way Efren goes to the table, that he is shooting instinctively. Yes, I may or may not be putting words in his mouth. I would say he approaches the shot knowing it will go in and does not calling out what slice or fraction he is hitting. I would also say he is not imaging a ghost ball. These guys approach on a line which stroked through will sink the object ball. I would say most(all?) pros are playing instinctively.
That is the end goal. . .to be able to remove specific aiming from your consious thought at the table.
Now, the system which gets you there, in a slump, is the right way to get back. So, a system is a good thing to learn.