We finally pulled the trigger and committed to a new SMB Sprinter! This forum has been incredibly helpful in gathering information and making decisions, so I just wanted to contribute back what little new information we've gotten about the current state of the ordering process, for any lurkers out there.
About the different offices...
We called up all 3 SMB offices, and all had long waiting lists out until around August 2017. Fresno was a few weeks longer due to their 12-week assembly line vs 4 weeks, but there were no short-cuts anywhere. Nancy at SMB-North was incredibly nice, helpful, and informative, but we ended up going with SMB-West due to proximity.
As has been stated elsewhere, the different offices have different offerings. SMB-North is more conservative about hacking up the base van, and doesn't support after-market upgrades to the radio or back-up camera systems, nor will they cut away a side panel for external access to a cassette toilet. Nick at SMB-West encouraged radio/camera upgrades, but not aggressively so.
About the Sprinter...
Given the waiting list, all SMB offices are already ordering the 2017 Sprinters, even though they're not on the market yet and they don't even have confirmed prices. So there's a bit of a leap of faith that the costs won't skyrocket.
The only known change in available options, compared to the 2016 Sprinter, is that factory swivel seats are now available on all chassis, not just the higher GVW ones. We were planning to get the comfiest chairs but only swivel the passenger seat, but as an options package it was supposedly more reasonable to just do both. (Another leap of faith!)
About our build...
We kept to our original plan
for a high-roof RB 4x4, despite some last-minute waffling about whether it was "too big". The prices add up quick! We selected nearly all the Comfort/Convenience options (except navigation), rear camera, trailer hitch wiring, and rear-window wiper & defroster. We likely will never use a trailer, but it's so much cheaper now than later and could kill the resale value if it's not present. I'm still a little unclear on how much of the MSRP we actually pay, but as they say, "In for a penny, in for a pound... of thousand dollar bills!"
We're still researching and debating some of the interior components, but nothing that affects the OEM options from Mercedes-Benz, so we've got plenty of time to finalize that, hopefully visiting Fresno in the fall to see them all in person.
The wait time is a disappointment, but that'll just give me a little more time at work to pay this thing off, if I can concentrate on anything else.