While I like your idea I'm not sure it is practical. Each guitar and bass library from a software company like
++ Amplesound ++ typically is more than 5 GB in size.
Exactly, which is why these 3rd party libraries get our dollars..,
.., ie; because not only are they far more customisable , but the detail is there .., for example I have a piano - (52 GB library) just for its 'one patch', but it has 21 ' accurately applied' (ie; not guessed) velocity layers , 10 randomly applied round robins , long note tails that you never hear get cut off or faded out if a note is held, High resolution Samples , and 6 different studio mic selection options to pick and blend from .
Whenever I go back to the 'factory type' pianos and compare (eg; UVI, Kontakt, Sampletank 3 factory libraries , or the libraries that come with DAWS etc) all I hear is a one dimensional bland lifeless Mr Robot piano
(even after they try to cover up that fact by drenching them with reverb) .
This is just one example .., I have 2 huge Piano libraries
(like the example described in the 1st paragraph) with both libraries representing the same brand of piano ..,
yet those 2 different libraries offer very different textures with one that will sit better in a rock / pop mix, and the other being more suited for orchestration , classical etc,
.., and were not talking about EQ settings here , The texture I am talking about derives from the actual body of the sound,
- created from the brand of mics used
( ie: each offering their unique sound from their brand and the individual positioning that mic ) ,
- the rooms vibe from the studio, the individuality / touch of the engineer / producer ,
- the pre-amps and console that was used, outboard gear ..,
ie; all this combined to created that texture 
.., and thats an example just for a piano library - then we have ALL those other
instruments with similar considerations which is why that market exists.
For this detail and realism - I don't mind paying and would never expect this kind of detail to be included in a factory library .