Rip-Mix-Burn for Feeds?

I have been quite enthusiastic about FeedBurner since the very first time I used it. I even did some coding using the various feedburner APIs and tried to integrate it with my appcliactions.

Then it struck me: we are in the rip-mix-burn era, rip-mix-burn should apply to feeds too.

We've got FeedBurner, that's quite good for the BURN part. Search engines like Yahoo!, Google Blogsearch, Icerocket, Technorati, del.icio.us and others provide us with many options to RIP information into RSS or ATOM.

What we don't yet have is a good MIX service. I would like to be able to mix two or more feeds regardless of the format they use (RSS, ATOM and variations) and get a single feed in the format I want. It would be nice to have additional options like "insert feed name befor title", or "include this feed as a once-a-day/week summary" (FeedBurner does this for del.icio.us feeds but it could make sense for Flickr "photo streams" and probably other services too), etc.

Anyone working on something like this?