The ideas you gave here are really good. But you know, we are making these assumptions by common sense, not excperience.
I would like us to actually have a look at previous rescue/fighter bots which have to be rugged, and powerful to at least maneuver on a rocky terrain.
For a start and to be fun I want you to see this video on Robot Wars. NOT SAYING WE FOLLOW THIS, but just to get an idea of the "size" when they look about 30 cm and 40kg, but in reality are BIg and about 100kg!!
YouTube - Constrictor (Robot Wars Battles) (Will blow you away!)
YouTube - Extreme 2 All Star Championship Grand Final (Will ... i have no words!)
YouTube - Robot Wars Extreme 1 Annihilator 2 - Round 1 (If you want to know the actual size @_@... unbelievable, it can eat a man....also see the house bot Sir Killalot! 216kg; petrol engine; lol )
This is just the start we will have more info here to study present designs. Ash, the steering mechanism is a good idea, but we will need atleast a 1/2 HP DC motor for each wheel (not sooo big), so for this to work we need good calculations which we will surely do. I will post more info here AND on celabs.tk under a new subpage "Case Studies"
Dude, watch that video above (as an example:: one robot consumes 700+ watts, 100kg)