Possibly the least nutty way of doing it might be to have them install S&S couplers. Apparently this is all done on a oneish off basis, and requires that they insert new tubes such as you require for your 30 mms. No reason why they couldn't do it, other than obvious production issues. For that mater, anyone capable of doing the welding could insert 2 new tubes without the S&S.
It would also be possible to cut and rejoint the tubes. Doing that would require some change in geometry since the longer tubes would take a slightly different path, Whether that could just be flexed into place is something I haven't tried and don't know. The whole thing could doubtless be buttoned back up, but it might appear that the tubes weren't completely straight because of the compromise geometry. If you are thinking of doing this yourself, then you might pick up a garbage days MTB of the rough same size and try the surgery first. If you want to braze in the patch it would probably take some 4130 stock and a lathe to make the parts you would want to slide in place. A drawing of the new geometry would also be required, since while your TT would be basically 30 mm longer your DT would be a longer patch. All pretty standard stuff.
At a metal level it isn't at all impractical, at a finding someone to do it, and getting it painted well enough to look like anything level it is a slightly more difficult thing to work out. What you are looking at is similar to what is involved in installing the S&S couplers, with the exception that there wouldn't be any distortion in the lower tube with S&S, and there isn't the cost of the couplers themselves unless you take my idea of contacting Surly and asking them to insert length while doing a standard coupler job. I'd do it if I was local, but moving stuff from the US to TO, and TO to Calgary would be just another cost burden to bear in the whole process. So when looking at cost you could check the price o the couplers, the price of adding them, and the price of Surley adding them, to get a ballpark range.
I gave some thought to doing the suggested build on a Nashbar touring bike. It has a ridiculously high BB, and they sell several forks that would work well and use disc brakes that would deal with half the brake problem. Of course most people don't favour those frames as much as the LHT so the end result might not cause the same comfortable feelings. I just wanted to see if it could be made to work, not really practical for me to do it for myself since I can get a decent tube set for a lot less than even the Nashbar frame.
Surly LHT, Surly Big Dummy, Surly 1x1, Surly Pugsley, Bike Friday Tikit x 3, Bike Friday NWT, Bow Cycle 24, Santa Cruz Nomad
Surly won't get involved in doing a S&S coupler install or frankly anything that isn't a catalogue item. I don't blame them - as they've got lots to do already. I'll take your advice though and see what Bilenky thinks as well as what they'd charge to do the work.
I'm also looking around at the existing 26" wheeled production touring bikes and seeing what else might work. I've got to factor into the equation that I could mod the LHT and not love the end result whereas if I don't like a production frame selling it will be much easier.