As far as I understand, a newer Sturmey Archer 5 speed hub has 20mm total cable pull and ~5mm between gears. A SRAM 10-seed shifter has 3.1mm pull between clicks. According to the chart on Sheldon Brown's site, the Jtek Shiftmate #6s has a 1.619 ratio.
3.1mm * 1.619 = 5.02mm
So should this work? Am I crazy for wanting to try this?
Retroshift would be a cheaper option if I didn't have a SRAM Rival shifter sitting in my parts bin. FWIW I'm currently shifting an SRF5 with a SA bar-end.