You can change the catcode of the upercase "T" and define it as a macro that peeks some characters to see if it if part of a "Therefore". This may break other commands that have the upercase T in their name, so it will create some random unexpected incompatibilities. (Many babel languages change catcodes to make accents easier to use, and therefore they create some random unexpected incompatibilities.)

More info about catcodes: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=activechars