I used to dual box CoH using two PC,two keyboards and two mice.

kind of a limited amount of boxing support there, had to manually target my main and then hit the follow key , which I think was F and I think that allowed you to target thru the main although I can't remember if they nerfed it for PvP

if you had hardware broadcasting of the keyboard to several PC you should be able to do it.
I would suggest doing 5x fire/rad controllers with your main character getting team teleport.
I was part of a guild that did this once and it was so much fun, we got to 50 in less that 30 days.

a 5x fire/rad team will MOW down anything in the game including the hardest settings.

once you get Accelerate Metabolism 5x all of your characters you will be at max +dps without enhancements and you will rarely be without it because the cool down is reduced 5x.
once you get team teleport you don't have to follow, your team teleport transports the whole team at once, imps included. you litterally POUNCE on the target.
once you get your imp pets all bets are off.... you are now a killing machine.
you just have to have everyone set to fire off some type of stun, fire cages and let the imps do their thing while on crack ( AM ).