There's nothing wrong with a message in a mapped key, telling you what to press. Addons can give you messages too. Prior to switching to IS Boxer (using Keyclone), I'd have Jamba send the message "Press G3" when the toon who was healed by that key got down to 50% health. The generic is, something like "I'm hurting" or whatever. I changed each toon's message to "Press this Hotkey", where each asked for the hotkey which would heal them.

The option do not advance to the next step, even if I push the key, is a little too hazy/gray for me. I realize you are still spamming the key, and every action your team takes is a result of a key press/release. In the current game, with commas in a castsequence (and consistent spam speed) this is the exact same as the option in IS Boxer. However, in the near future we lose the ability to time our recast delays via the default interface... at which point, using software to achieve what Blizzard has intentionally removed is a circumvention I'm personally not comfortable using.