Feature request from chasteIT, posted on GitHub Sep 03, 2015
Filtering items in grouped product grids using the attributes of their associated simple products could allow users to select options to find their desired simple products similar to configurable product selectors, but it would also allow the store owner to display all of the available simple products initially.
For example, a Grouped Product could contain TVs of brand Samsung, Vizio and LG available in sizes 50, 55 and 60 inches. Upon entering the page, the customer could see the grid of products and their varying brands, sizes and prices. The customer could then select options in a dropdown filter to only show their desired brand and size.
A sorting feature for the initial grid would also be cool.
Edit: I found Magneto extension, Grouped Products Filter, which does this exactly. Here is the demo.