If it were me I would look for modulation souces of randomness and probability you can do something simple like using NLC Sloths to modulate Ochd or add small utilities like Noise Engineering's Clep Diaz for some clocked but random modulation, the 2HP RND is a good one and doesn't take any room up. I quite like the Befaco Burst because it has a probability control and a lot of control over its bursts though it is Clocked so expect a regular clock tick to come out of it which usually works for me but i sometimes wish it wasn't there when I want less structure. You can get little CV and gate generators like the ST Modular Isi Wren which is surprisingly useful for Rhythmic control of Filters etc.
You can't knock an un-clocked Mutable Instruments Marbles with its range of CVs and Gates.
Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.