Thanks to Steve Swinsburg, Nuno Fernandes, Noah Botimer, and Matt Jones, I now have shape-shifting poms in my BasicLTI. It can compile in 2.5.x or 2.6.x/2.7.x by changing the version in the parent pom in the top pom.xml in my source tree.
Here are the relevant very well written blog posts:
http://steve-on-sakai.blogspot.com/2009/03/build-profiles-and-sakai-dependencies.html
http://codingwithcoffee.com/?p=135
http://steve-on-sakai.blogspot.com/2009/05/build-profiles-and-sakai-dependencies.html