One thing to note: if you plan on starting out with MBW: 2 and upgrading to MBW: 3 later, you can always start with a Reaction of 4 (improved to 8 ), then, when you get the MBW: 3, also get Genetic Optimization: Reaction, which allows your Reaction to increase to 10.
Don't forget the positive quality that increases the stat maximum as well. With the genetech mod and that quality, you could end up with the full 5(11) Reaction from MBW3