personally I would keep Maths - download the 'maths illustrated supplement' and work your way through it, it is a great primer for patching modular synthesizers in general
I would take disting from the lower case and take everything out of the 3u row of the other case except maths and fx aid xl, then add a quad cascading vca - such as veils and a full size plaits - which would leave 12hp - branches will fit in as you already have it - pick up a kinks whilst you can - there is stock in some shops but they are discontinued and great value for money! - leave the last 2 hp free until you work out what you actually need
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities