Honestly don't see how it's significantly harder than alt tabing between characters. Alt Tabing involves using two (or in my case four) characters at once, moving them manually, casting their spells manually, and then switching to another...

If anything this would be easier to do, since you don't have to switch characters, once you got used to it. It's impossible for it to be less effective than alt tabing, since you could always just use one at a time.

I know while alt tabing boxing I've wanted to move another character, and not been able to.

I don't think this would be terribly difficult, the only major obstacle would be learning to mouse with my left hand.