There were a few problems with the ES1.1 (2003-2006), as not only were the soundboard sensors going bad (not rare, from what I heard), but folks complained of rattling AA batts, and wrapping them with a post-it-note was not uncommon. And yes, I had an 04 ES go bad, but I simply had it repaired (by an auth. tech) with the same ES as it was long ago before they had the newer versions.
Upgrading from the AA to the 9v system requires some
wood work on the end block, which is why I suspect Taylor wont allow a tech to upgrade it and they prefer to do the work. But the upgrade from the 1.2 (2007-2009) to 1.3 is an easy operation for a tech, not to mention I had it done to two guitars by my tech. Just offering a data point to consider
Edward