I'm struggling to think how EA could empower Manual controls to enable you to play 'better' than with Assisted controls, beyond what is inherently there. How could they change this?
Manual has some advantages - primarily in that it's a lot more free. You can do what you want with manual. With any assisted set up there are things you simply cannot do. You are always constrained by the artificial intelligence which picks the passes for you, which is often quite hard in itself to predict.
So in that, manual has an advantage, because it gives you more control, and more control is useful. Manual, even now, is not so much less useful than assisted, if it wasn't for a few areas where the assisted passing is really, really dodgy (like 180 degree passes, and the over-the-top throughballs).
But manual could be helped to make it easier still: one of the biggest problems being the charge up time for manual passing. I've suggested a solution to this, where the direct/through pass buttons were differentiated under manual so there was no overlap. For example, the direct pass button would do short passes, and the through pass button would do longer ones. This way a short powerup can give you a lengthy pass, and you have a lot more precision over passes, in particular the short ones which are quite tricky as of now.
Maybe manual can never be made as effective it should be, but it isn't that far off now and there are areas it can improve on (and a few where it needs to be made harder).
Surely the problem with assists is that there's no/insufficent error factor built into the game to begin with. Fix that, then would the control setup even be a problem?
Depends how the error is applied. I'm adamant that the manual error would need to be less (to compensate for the human error already there) than it would for assisted. Reasonable human error + contextual error = realistic error, should be the standard applied in all situations. Obviously, if human error is bigger than realistic error, then there is nothing you can do about it.
For example then, a difficult pass with Fabregas should maybe go roughly where you point on manual, should have a bit of error on semi, and a bit more on assisted. The same pass with Gary Cahill should have a bit of error on manual, quite a lot on semi, and lots on assisted. Something along those lines.