Well, I haven't been able to try this out, due to me having a mac

but, I'm going to look into setting my old rig up to try this out, if you think it's a good idea.
Thanks for the support, not the instant "It wont work"
But, I'm sure it would be a little something like this:
1. Setting up the ps3 so that the ingoing and outgoing network is through your computer
2. Sniff for connections through the proxy program
3. When the connection is valid, stop the download of the patch, and send your premade one instead.
Only a theory, but this will make sure that the PS3 is open to recieve packages, but I'm still not sure if the patch_mf file is downloaded during the patch?