If you keep the servo brake and don't want reverse, why not keep the 2 speed? You won't have to do the lock mod then. That will let you run a little more aggressive gearing (like 40/16) to give you good top speed while first gear will help with take-off power. Actually, the Revo will probably run better like this since your gearing matches the motor.
If you have the tranny open anyway to do the FOC, you might as well do the pin mod; just prepare for drilling a slightly larger hole in the shafts since they are steel (high speed and light pressure). You'll also want to slightly enlarge the hole in the gears otherwise the slightly larger diameter of the pins may crack it if you try to jam those Jato pins in there. But I think the stock pins should hold up with that motor, but don't quote me on that.
So, this is what I would do:
- RCM motor mount
- A few
Jato outdrive pins. Not sure if you can find just the pins...
- FOC
- Whatever battery you want (4s is good)