I want there to be a separation of the style sounds from the left/right hand sounds.

So that there are sounds for the master keyboard that we can use for live playing.
The sounds for styles are in a separate place.
With that, You can have for example, a set of 200 sounds that would only be used for styles. Now the manufacturer can commission style programmers to create hundreds of styles for that sound set. Then you sell the sound and style pack separate from the master keyboard maybe as a software download or an expansion card.

So take the G70 for example. I think it has 2 expansion slots?
On one expansion card, you would have a set of sounds that are used exclusively with those styles on that card.

And, if all brands were to have this feature, you could interchange the cards between keyboards.

It is kind of like all stereo sets are different (they have different eq and play back settings) but they can all play CDs.