Consider the following major revision:
I've kept the sequencer, filter, reverb, delay and output. I've replaced your LFO, oscillator, VCA and envelope with two oscillators, a dual VCA and a dual envelope. I've also added a multiple and a mixer. Good on you for thinking to put in an output module by the way...a lot of people don't think of that and it's a good thing to have.
By swapping the LFO out for a fully featured oscillator, you get the option to use the second oscillator as an LFO or as an audio source. The multiple is added so you can have both oscillators follow the same CV if you're using both for audio. You can use the mixer either to mix the two oscillators, or if you're not using it to mix oscillators you can use it to mix control voltages. This really isn't a big enough system to really warrant a voltage-controlled envelope, so I swapped that out for a dual envelope generator. Finally, I swapped out the single VCA for a dual VCA.
I don't know whether or not the case you're looking at includes a power supply, but if it does make sure it supplies enough power and has enough connectors (8 connectors for the system as you laid it out, 10 for the system as I laid it out). If you don't have a power supply, you'll need to sacrifice the effects modules (the reverb and delay) in order to have space to put in a 4HP power module.