Well, if the objective is to keep this very West Coast, I'd yank the DPO altogether and put in a Maths instead. Since Maths is a complex-wired version of what's basically a Serge Dual Universal Slope Gen, it fits. You can use the two slope gens as modulation, or you can cycle them at audio rates for extra VCOs. Lose the buffered mults; you don't have enough tuning-critical signals in here to justify their expense, and the rig itself is small enough that inline mults or stackcables make a lot more sense here. With those removed, you then might want to put in a 2hp delay to go along with the 2hp reverb (since reverb was key to the Buchla sound, and delay [via the Wilson Analog Delay] was a significant part of the original Serge sound). And since these simpler modules are "appropriate", then you can remove the DSP as being more or less redundant.
Another redundancy might be found with the A-149-1. The Wogglebug is actually an augmented version of the Buchla Source of Uncertainty, so having two of these is a bit much. The A-149-1 is also WAAAY too deep for a Rackbrute cab; you want to keep your module depths around 40mm or less so that you can have space for your ribbons and airflow inside the cab. With that gone, you might then want to add a stereo filter to tone-shape your mixer output; while VCFs that are typical to subtractive synthesis aren't 100% "West Coast", adding something that can act as an overall timbral shaper would be right. Have a look at WMD's Overseer, for example. It's not a "normal" VCF, but if you used it post-mix as a timbral control (either manually or modulated) that would be more in line with what the Buchla 291 is for, especially since you can CV the response behavior which makes it act more like the 291e's "morphing" capability.
Last, something additive as a VCO. The Verbos Harmonic is nice. It's also HUGE and as such, isn't really appropriate for a small build. The Mannequins Mangrove, however, is only 10 hp and while you can't directly address individual harmonics, you still have quite a bit of leeway in manipulating harmonic content with it.
This should be a lot more spot-on with the West Coast model. I am wondering about that MScale, though...if this is in an Arturia cab, wouldn't it be linked with a Minibrute 2 or 2s and not a Moog? Or does the MScale deal with a Moog that's somewhere else in your rig?