|Storing all the incremental diffs for all packages is not necisarily more storage… provided the delta’s are small.
We already have 3 versions of most packages in the pool; stable, testing, and unstable. Using delta storage could actually reduce the storage requirements if the deltas were small enough. It would also be fairly cool as you could pull out any version of any package. Have a look at xdelta as a pretty cool delta storage filesystem.
The problem is “if the deltas were small enough”. The best generic xdelta’s on debs are _not_ small. Using rsyncable gzip would help, but I suspect binary executables would be still be very different. Even a highly specialised deb delta tool would probably not buy you much over rsyncable gzip.
For delta storage to be even worth considering, I would guess that an average delta size of 10% would be required. This is easily achievable with source, which is why CVS is a popular way of storing source. It is not so easy with binaries.