The numbers look good. But...........there's always a but. LOL
That's one huge gear ratio. 2.85:1
You've chosen a lower kv outrunner. A big one, and that should help. Running it on 8S will get your top speed up to the really fun range.
You need an ESC with a great startup routine. I don't have any experience with that one. Metalman does I believe.
On the brakes, this is where you have to be creative. On my Revo, I had considered moving the mechanical brake to the diff pinion. There is a kit for the Revo that allows for this. I wonder if there is something like this available for the T maxx?
May I suggest a diff upgrade? I would say that a pair of hybrid diffs with the buggy ratio gears would be a good idea. I do not think that the stock maxx diffs will be able to hadle the power of torque. Mech brakes would not be too difficult to do, but you would have t make a bracket to go across the chassis and hold the disk in the correct orientation and old the brake actuator.
Sounds like a fun project, make sure that you post pics! I will finish the hv tmaxx as soon as the brake linkage comes in at the lhs, been waiting 4 weeks, lol!