Wouldn't it be way better if Sage did not ship as a gigantic bundle?
This has been discussed over and over again and it plainly doesn't work. The Sage in Debian does not pass doctests, not even close. In general the combinatorial explosion of configurations to debug is way too large and it is next to impossible to find any distribution where the version numbers even remotely match. We updated to GAP 4.4.12 in Sage 3.3 and the doctests involving GAP will in certain files be broken with any previous GAP release. If you used the Debian packages for Singular Sage won't work since we patch NTL and when those NTL libs come in conflict either Sage doesn't compile or Singular blows up. I can go on and on and on about similar issues and that is only the stuff I know about right on top of my head. I have never taken the time to go out and do dumb things to break Sage
In the near future we plan to upgrade to a svn release of the development version of pari and then closely track it as bugs we report are often only fixed in pari-2.4.3svn. There is *no* way any distribution can track this without potentially breaking other code dependent on pari and you will be royally screwed if you want to use pari 2.3.4 in Sage (the stable release at this point) since Sage won't even build. We will fix all in tree code that gets broken with the new pari-svn and push it back upstream, but until that shows up in a distribution we will long have shipped Sage 4.0.
The way we do it is the only way and I have doubts that any distribution packaged Sage will even be able to keep up with the official release given that I (=Michael Abshoff) spend working full time as the Sage release manager