I just thought of something while browsing ggdeals.
I was looking at the Total War II Collection on Steam, which is a pack of the main game + all DLC.
Currently, this pack on Steam is more expensive than buying all items at their current lowest price one by one on other key resellers.
But, it would be so much more convenient to have something adding up the current lowest price of all items in the pack, and then comparing it with the price of the bundle. Then it could say how much you would save by buying separately compared to the pack, or the opposite.
This is basically what Steam does with its own bundle, but it only compares items within Steam.
That would be a very nice option I think 🙂