Are you still doing a third row?
If you do a third row, it should be entirely utilities/modulation/VCAs/attenuverting. Maths is a good one (though it's not a VCA). Free-running LFOs, envelope generators, sample and holds, random modules, and more will give you interesting freeform contrast to the more steady rhythms from the sequencers. These are all cool sound sources, and if you perform with an Analog Rytm and/or Syntakt as well, this should just about work, but you need more stuff to make it all move. More than anything else, moving voices and sounds around freely and uniquely with modulation is what makes modular sound special relative to regular complete synths and grooveboxes.
I would also take a look at bigger, more playable filters. Big cutoff knobs. Or at least put those near the ends so they're easily accessible.
You don't need dedicated drum modules unless there's a specific one that does something you love and can't do any other way. The BIA is actually a good one for a tightly packed case like this since it basically operates standalone and is very flexible, doing way more than just standard drum sounds. Generally, though, it is just as easy to make drums from a basic synth setup (oscillator into VCA/filter opened and closed by an envelop or other CV) as it is to make a synth sound with them, and modulation/clever patching can help you blur the line in unique ways. You can even get a matrix mixer to help you smoothly move and combine modulation in your rack to change stuff from melodic to percussive.