I think it would be a good idea, but the heroes you're looking at would be odd... I mean, having orcs involved with the NE's? Even at this point in the Warcraft universe, their alliance is tenuous at best... I think using more general heroes that fit into their races (BE/Naga, or NE) would be...
The Tower Defense might have had it so that buildings are affected by Auras--there's some way to do that, but i can't remember exactly what it is, that's what the experienced map editors are here for :)-- and so the towers would have gotten damage from Thorns Aura. I don't think Thorns usually...
da1nONLYEd's right, you can't rotate a building, and you can go into the Object Editor, remove "Is a Building" to then rotate it, but as long as you don't need it to be built in the game, you can go back into the Object Editor after you've rotated it and re-make it into a building so everything...
There's a pretty good tutorial on TheHive about how to use substrings, but I don't think it contains everything that you're talking about-- he's got unknown substrings, but not known ones...
http://www.hiveworkshop.com/forums/f278/using-chat-commands-34686/