I've been looking at modular for a while, and tried to read and learn as much as possible. Here are the current plans for my first rack:

My goal is to both have some form of generative functionality, while also being able to create ambient background music. I have other instruments and such, so this is mostly just a fun additional thing to play with.

Am I missing something obvious in this rack? Any glaring faults or problems?

Please paste a link to your rack. It is easier to see the function of each module and to be able to comment on it.
ModularGrid Rack

As you will read in most posts, a bigger box. Maybe a 6U or 7U, if you like 1U modules.
It all depends on what kind of sound you are looking for.
At first glance, from what I see, all your pitch sources are random, coming from Chance, think maybe include a small pitch sequencer, to have more melodic control.
For example https://www.modulargrid.net/e/noise-engineering-mimetic-digitalis-black takes up little space.
It would not be a bad idea to also add an LFO with CV and resettable additional to Maths, they are affordable modules, they consume few HP.

I updated the post above with a link to the rack.

Thank you for your feedback. I will look into the Mimetic Digitalis. Any specific LFO you have in mind?

Something worth considering is to go with the Expert Sleepers FH-2 and turning the Disting mk4 into a Disting EX. Getting the FH-2 is simply to make space for the EX. The FH-2 may not be what you want in this case in which case this would be moot but it seems like they would have the same purpose for this system. The EX is basically the same as the mk4 but it is 100x easier to use. If the FH-2 works for you, I would do this. You also get the benefit of having two mk4s in one.

In regards to a pitch sequencer, which I do agree that you should probably look at, it depends on what you'd want. If you have something like an MPC One you can pretty easily use that. Same with a midi keyboard. A common one that is used with modular systems are the Arturia Keysteps. The Digitalis is a good small option.