A lot of the key to that, IMHO, would be in your filter selections. You'll want some LPGs (I suggest Make Noise's Optomix) to add that plucked, woody Buchla-oid sound alongside the 2s's Steiner-Parker-derived VCF. For the other, given space and cost, I doubt you could do better than G-Storm's Tonus VCF, a copy of the tried-and-true ARP 4012 "pre-lawsuit" VCF. And in both cases, you get two-input mixers thrown in for good measure, which cuts out some of the need for mixers for your VCOs.
As for a replacement for the Shapeshifter, you might consider a pair of Mutable's Plaits...two morphable digital VCOs for less than the other, in 24 hp, still saving you 2 hp for something else. And for reverb, look at Purrtronics' Purrvrrb...a mono-to-stereo digital spring (the classic modular reverb) emulator in 8 hp for only $130, then you can also add a delay like the Chronoblob II for $250, giving you stereo reverb and delay in the same space as the Erbe-verb while coming out over $100 ahead.