The main reason Truggies dont run 2 speeds - is its not legal for racing. Also you need the center diff to be able to split power, not to mention dampen the loading of the drivetrain, so that it does not take its toll on the chassis and other components.

You are right its worth a shot if thats the avenue you want to approach, yet it will also affect handling overall. Give it a shot, I am sure the GT 2 speed would be able to work. Also keep in mind that .28 will also be more aggressive on those gears of that 2 speed. Just a few thoughts to consider.