I like the modules you choosed.
I think its a good starting point but more stuff will surely follow
PPl will say: "Get a bigger case"
Agreed that it's an interesting collection of modules to start with. Also, let me be the first person to live up to MCGM's prediction: you'll probably end up wanting a bigger case, sooner than later (no disrespect to the intellijel 4u intended). Building a small focused rack is certainly doable, but it comes with sacrifices and really requires you to know how to get the best functional bang for your buck hp wise. Again, totally doable, and you can build an amazing instrument in your selected case, but as a beginner the restricted hp makes things more difficult. Plus, despite what everyone tells themselves, eventually GAS will strike and you'll want to try something new that won't fit. Personally, I'm fond of the mantis cases, but there are plenty of others out there to consider.
More utillity modules like attenuverters, matrix mixer, offsets, vcas etc
You could add a dedicated filter even if the Ghost has one integrated
Vcas-- MCGM
Agreed with all of @MCGM's comment, but really want to highlight this part. You'll get a whole lot more out of the modules you've already selected if you invest in utility modules like the ones listed, especially vcas. Let me also recommend LFOs. Something like the Ochd and it's really useful expander is great for slow organic changes.
As a side note, how were you planning to use the quantizer, was that for the Steppy? Quantizers are cool, but unless you have a specific use in mind, maybe not the best fit for the collection of modules you already have listed (the Pams can do some quantization, for example).
Anyhoo, good luck!
Edited because I made a typo.