Tires shouldn't be a problem, I would check with Discount Tire Direct or Tire Rack and let them know what you have in mind. If they're of no help, I'm sure you'll find a Rally forum that will have a LOT to say on the subject. Oddly enough, I've been told snow tires do quite well on dirt...
As far as the light bar, that would likely have to be either fabricated or adapted from something similar. Could probably run a mounting bracket through the opening in the grille (the big opening, not the little one between the turn signals), and put the lights right in front of the bumper itself... If you're running an NA, shouldn't interfere with cooling or anything that way.
Now, suspension... I honestly have no advice for you here. You're going to want a decent amount of travel, and probably a fairly stiff setup to deal with sudden drops so you don't bottom out. Might even have to go as far as using spacers to raise the ride height up a bit. Not sure how much alignment flexibility these cars have when you're raising the ride height, might run into the same problems the drifters do with these cars. MPR (another forum member on here) might have some suggestions, I believe it was him who posted a picture of his old Civic...
Anyway, good luck, and if you really go down this path, you gotta post a thread about it! I for one would think it could be badass.