I actually have all of the modules in the rack I originally posted and...

Sorry I misunderstood. I thought you were just thinking about accquiring these modules.

Now I see the following ways going forward - depending on your (financial) commitment to eurorack:

  • Sell some modules on the used market and replace them in your rack (one after another).
  • Get a new rack, which is at least twice as large as your current one (13U, 104hp), replacing your current rack. Rearrange your existing modules and fill up "missing" ones gradually.
  • Get 1-2 new racks and plan them "in a modular way". Meaning, to have different racks dedicated to different tasks. E.g. first rack holds stuff for drones and 2-3 "ambient voices" (whatever this might be) - second rack holds 1-2 lead voices and drums/percussion - third rack holds complex sequencer, fx, downmix-utilities and controllers
    Rearrange your existing modules and extend the racks as needed.
    If the first (ambient) rack would have a noise-generator and a (simple) osc with some cv, you would already have some inreresting percussive sounds to play with while not necessarily needing more drum sounds (dependent on your desired style). Together with the sequencing-rack, you would have a nice setup, even for a live gig. (Many cases have the posibility to moint 2 of them together.)
  • or combine the previously described approaches in a meaningfull way

On another note: You might want to think about your requirements for the drums. Do you really need them in eurorack format or do you enjoy "more traditional" drum sounds? - e.g. you could just use something like a TR-8S
next to your modular. This would be more cost- and place-efficient, than building similar features out in eurorack-format.
Or you could use a Black Box (by 1010 music) as a sampler for drum-duties and sampling in general (but with less modulation options, than if it were a sampler-module). This nice little thing is even compatible with eurorack-levels. Adding a midi-module could enable you to use the box also for sequencing.