I spoke to John and he confirmed that the fermenter would be fine with the 3-4 psi needed to push the beer to kegs, which is all I really need it to hold (no intention of naturally carbing at 30psi in there, the potential for boomage is way too high). Add to that, John was pretty flexible in terms of customization, I wanted a 4" sanitary fitting welded to the lid, for adding hops and whatnot, and then welding a 1" fitting over the usual stopper hole, so I could add a triclamp blowoff, similar to what's available for the Blichmanns.
The only issue I have is the timing. Six months is just too long to wait for me to pay out the 70% deposit. I understand it's out of John's control, and when the time comes to add to my stable, I'm absolutely giving him a call, but for the first one, looks like I'm going with a Blichmann, and having someone weld some fittings on there down the road.