In order to avoid having BatchPatch download the updates, for what you are describing I would suggest the following:
1. Create a BP URL list for the Win 7 updates.
2. Write a simple script that looks at each filename in the BP URL list and compares it to your directory of previously downloaded updates. Have your script then copy any matches it finds into a new directory.
A different option would be to go into your directory of previously downloaded updates and sort them by name. Then manually copy any desired files – perhaps the ones for Windows 7, into a new directory. Then set this new directory as your BatchPatch cache folder. Then download the entire repository of Windows 7 updates to that cache folder using the BatchPatch download updates repository option. This will skip downloading any files that already exist in the destination.
-Doug