>>>If anybody has upgraded from a 3 speed sturmey archer to a multi-speed gear set for touring on the Brompton folding cycle, would they possibly have any information about how to accomplish this?<<<<<
I know some people who changed to the six speed but that won't make it a touring bike. Probably the only company making true touring bikes that have folding capabilities is Bike Friday. The six speed Brompton does not give you enough gears for touring and the geometry and small size is less than desirable.
You can get Bromptons with 7speed hub as standard. Im not sure about a Rohloff 14 speed, but that is probably too expensive.
There are specialist folder sites, like AtoB, which will direct you to specialist Brompton sites.
Brompton is the best folder for carrying on transit, and short hops to the station, but it is not a touring bike. You can ride them on longer rides, but if this is your intention, you are better off with a different design.