Some interesting ideas. TBH, if someone wants to do a bush mechanics course then just wait until someone blows their CV and have a look at what is done/ask questions/get stuck in. I think a welding introduction, including bush welding may be more popular.
Old tyre filled with concert up a steep hill may sound like fun to some but there will be plenty of people not willing to do any damage to their truck. Also what happens when you only get halfway up, reverse over it? Recovering it from a ditch etc (with concrete) or a tyre pull (without the concrete)in the woods could be interesting.