The Heritage line center channel speaker would be another Heritage speaker.
For instance I had 3 La Scalas up front. I could have done a Heresy, Cornwall, Belle also. The best way is to match all 3 Heritage speakers up front.
From the pic I saw of the Academy there is no mid horn just a high freq horn so the Academy does not seem a good choice for the Heritage line.
Also the Heritage line has always been marketed as a 2 channel stereo speakers that customers have used for home theater. Klipsch probably figured if the customer wanted the Heritage line for home theater they would just use another Heritage speaker for the center and rears.
Now you could contact Bob Crites or others on the forum and order the parts for a Heritage speaker and build a center chanel speaker. I have seen some on the upgrades and Mods section of the forum.