The harder part is the autoconf magic required for the switching, and not even writing autoconf (at least not yet), but rather incorporating the changes:
On my system, "./reautoconf" does not work, instead complains:
autoconf: invalid option -m
Two options: 1) install autoconf-2.13 and use that 2) try the same in my current tree (available from rsync://tug.org/tetexdevsrc/). That tree is already converted to autoconf-2.5x. Given the fact that Peter Breitenlohner has already worked out how to convert all packages that are part of teTeX (his work is now included in teTeX's new source tree), it should be fairly easy to make the same for the rest of TL, too. I honestly hope that the next version of TL will no longer use autoconf-2.13. Thomas