Is there any technical stumbling block to creating a UI mod that uses a private chat channel to send commands to your other alts to trigger spells and commands?

I am thinking of something like a pet bar, that allows you to control your alts without having to use 3rd party software. I don't see any reason something like that would be against TOS since nothing is automated, its still a person typing on a keyboard sending commands.

I'm thinking something like how GEM works with it's custom chat channel to send data back and forth. The tricky part would be getting the UI to perform the actions on the slave characters.

Has anybody tried something like this? It would make multiboxing much more user friendly.