is the tank stainless, and is it profiled at both ends? ie in your three snaps, are we seeing two shots of the same end, or both the ends?
if its stainless, and the ends are both formed, i guess the only way to do it would be to chop a band out of the middle, and get someone to TIG the two halves back together again.
if you found someone with a large enough lathe to cut the tank on it as well, it would make for a much easier cut to rejoin, with less chance of distorting the cylinder when cutting.