Yeah, I think this would be a very difficult job to make a plugin for Arch. Considering that you have to guess where to use the spell, and it has 3 flashing lights which indicate how close you are. I'm not saying it's impossible to do, but more so that it would be extremely difficult and time consuming. And, to be honest, I'd rather have a fully functioning copy of GB and HB more than a plugin to do Arch. Just my opinion.
Not going to argue with you there, however, who said you have to choose?
Buy yea. Was just thinking about it. IF it would be possible, it would probably not be in the near future.