Hi,
Good choice.
I have the Warna and is good for mult (and sum) pitch signals. For mult gates or cv I use passive multiples (less money and less space).
Filter. Your voices have filters yet (Mother, Oxi and OneRoi). I'll buy a filter just in case you want to add a new "simple" voice.
I like Bastl Ikarie and Three Tom Steve's Ms-22, but filter are a very personal choice.
Modulation. Maybe some random cv generator. LFO's and enevelopes are good for modulation, but are "statics". If you want more rythmic modulation maybe a Sample and Hold, for example RND STEP from DivKid, 6 channels in 4HP. For dynamic modulation, maybe a classic, a MI Marbles clone.
Best regards,
Ferran