Dave, great summary of the trip. Wheeling the Rubicon in a heavy wagon is the best! You are right about the extra traction with the heavy wagon. Those little rigs, minis and 40s, like to watch the heavy beast on the trail but if you get stuck and need a strap or tow out they'll run for the hills.

At that point, another wagon will be your friend.
So tell us which tools and spares got used or loaned?
What did you wish you had?
I always take a ton of stuff even though I try to pack light. Some items not mentioned include:
Splitting Maul (sledge hammer) - great for going caveman on whatever needs a beating. It gets used every trip.
Jack Stand (or two) - Very popular for added safety during axle work. Again It gets used every trip.
The other, which I think was mentioned, is electrical test and repair goodies. Multi-meter, wire, connectors, fuses, bulbs, tape and automotive relays (very popular). At least this stuff is light and compact.
Finally, this might be more of a mod than a spare or tool but I really like having "Speedbleeders." Makes one man brake bleeding easy. Oh yeah, the spare brake fluid and a piece of clear tubing for the bleeder are always popular too.