This is possible but perhaps not easily with a macro you can drag to your bars since regular actionbuttons don’t do an action on both down and up unless you button:RegisterForClicks(“AnyDown”,“AnyUp”). This creates a dependency on your action bar.
This post has a small addon that makes SHIFT-C run two different macros, one on key down (to start heroic leap reticle) and another on key up (to cast heroic leap @cursor)
You can modify it to cast thunderclap on key down and revenge on key up.
/castsequence would never progress beyond the first spell if you had a reset on the key up. So I’m not sure what you’re after with that. Unless you think keys would repeat while down? That doesn’t happen.