Hi Radi,
Having discussed your suggestion with the members of the scenery models data base maintenance team, I can tell you there were a few methods considered for sharing textures between models.
I won't bore you with all the details, but the main stumbling block is that however/wherever the texture is located each model that uses it will call it up separately.
That means each model is a separate object. There is no way for this to be changed and as such, there is no process or time saving.
To make a major change to FG processing/coding, there has to be an advantage in making the change. Having the texture in the same folder/directory as its model (as they are now) is the shortest possible path.
However, please don't be put off making suggestions. Someone has to have each new idea, so why not one of yours?
Cheers,
Vic