Wow that was alot of reading back and forth of the same thing over and over again!
I had to wait till I was at a computer to reply to this as I didn't even want to attempt this on my phone lol!
Here are my 2 cents on the issues that have been laid out here.
RTR vs Kit
Punch out a RTR version FIRST!!! You would not believe the people I have seen go to the onsite hobby shop, buy a RTR SC truck, charge up a pack and put it on the track. Getting into this hobby initially, I got a RTR Stampede way back in the day! I learned to repair what was broken by taking it apart and cleaning and maintaining it. I can't count the amount of vehicles that get brought into the LHS and put on the consignment shelf due to the owners getting frustrated trying to build the kits. If you look at Axial, almost every vehicle they produce you can get in RTR or kit form. Case in point, the new Yeti is a RTR with a 4 pole brushless setup. All that for $429!!!
Durability/Performance vs Scale
You are making a solid axle MT, you are already going down the scale route here. If you throw in big diffs, the housing are going to get disproportionate. The Wraith axles can be beaten into submission but they are also very strong out of the box. I have hammered on a RTR wraith with no breakage. This all goes back to maintenance. Make sure the screws stay tight etc. I don't know the best route to go with the tires. I would say stick with the clod size tires. I know that everyone has said speed sell, in my part of the world people say "look at them big 'ol tires!"
I don't know how many of you follow the crawling aspect of the hobby but you might be surprised to know that Axial has seen a pack of mega trucks running at their biggest event, Axialfest, this year! I was there and watching intently!
Anyway, that is my 2 pennies. Take it or leave it, that is what I think!