I think you guys are getting a bit ahead of yourselves

Two things need to happen for it to be realistically boxable, neither of which have been answered: A) Will Bioware even allow multiboxing to exist in their game? and B) Can multiple instances of TOR be launched on one computer and run properly without modifying the game files?

Until we get an answer to those two questions we should probably skip over the more specific issues like class combinations and difficulty of leveling. In the end, if the two questions above are answered yes and given what else we know about functionality (follow, assist, group size) then we can make it work. If Bioware says "no" or you can only have one instance of TOR running at once on a single computer then it really limits what we can do.