The process of splitting (and disassociating) coins post-fork requires user input at several stages in order to properly protect oneself. Armory is an expert level wallet where security is always considered before convenience and as a long time Armory user I can comfortably say that I would never use such a "magic button" and would hope that the Armory dev(s) would never consider wasting time implementing such a feature. Bitcoin itself is a advanced course in personal responsibility and trying to push that responsibility onto others typically leads to monetary loss.
Security <--------|--------> Convenience
Choose one.
Also, the first post of this thread is still relevant.
Absolutey this.
Better than I could have put it.
Ente