Oh, good lord...
You ORDERED this? First up, you have things in here that will NOT work in this configuration. The Doepfer "mixer", for example, isn't going to mix ANYTHING without the output stage. This is also VERY dependent on the 0-Coast in there (where it really shouldn't be, since 0-Coasts have their own cabs and power) for filtering, proper envelope generation, and so on.
This is "sexy module syndrome" taken to the usual, horrible extreme. What boggles my mind is that you admit that you don't know what you're doing, BUT YOU BOUGHT THIS ANYWAY! Yep, you'd better be anxious...because it's probably going to take ANOTHER Rackbrute 6U to house modules that can make this build work. Far as I'm concerned, you've made a grave mistake in dropping a wad on this and then expecting to get a workable synth. You won't. The only thing in here that's useful is, in fact, the 0-Coast...which you might've just gotten in of itself and learned loads more than this rack will provide.
If you can cancel the order, I'd suggest you do so.
-- Lugia
This is needlessly hyperbolic. There are plenty of people who come in here planning a 104hp skiff that is Morphagene + Mimeophon + Arbhar + Magneto + Hermod, with no idea how it will actually function. That is "sexy module syndrome taken to the usual, horrible extreme." But this system is nothing like that.
These are all perfectly functional choices, aside from the mixer... there are just a couple things missing (others have given you great suggestions on that front). Taking the O-Coast out of the rack will provide more than enough room for those modules. You do not need to add "ANOTHER Rackbrute 6U" to make this a terrific small system.