First thing to do is completely remove any thought of including the Mother-32 in your Rackbrute:) It is a huge waste of HP space in an already small Rackbrute 6U (which I have). There is actually a calculation that you can do to show you how much extra $ it costs you to put something in your rack that can be left out of it...like the Mother-32. With the location of the patch bay on the Mother-32 and the way the Rackbrute stand is designed, you can just locate the Mother-32 in front of your Rackbrute (I do this with the Hydrasynth desktop.
As far as what modules to include, Maths is a good choice...I can't tell what the other ones are in the picture. Consider Veils and FX Aid XL for sure...and other utilities like Links...maybe some additional modulation sources like Quadrax. Others on the forum will be far better at providing information about what modules to include
JB