In a true virtual grid, the GridControl (and hence GridModel) does not really store anything. It serves strictly as a conduit to the virtual data source. So, instead of thinking about have multiple GridModels and 1 GridControl, I think it better fits the grid's virtual architecture, to think about multiple DataSources and 1 GridControl.
Here is a little sample that illustrates this idea. Will something like this serve your needs?
VirtGridMultipleDataSources.zip