Looking for a narrow-cage 16T capacity FD
There will be only very small differences in the widths different FDs (assuming you are talking about the inside to outside dimension). One that is designed to be minimum sized so that it provides a best fit for 46t large chainrings is Shimano's CX-70, intended for cyclo-cross:
http://bike.shimano.com/publish/content/global_cycle/en/us/index/products/cyclocross/cx70/product.-code-FD-CX70-B.-type-.fd_road.html
It does have a 16t capacity. It is also compatible with the bar ends (which don't index the front anyway).
I have purchased one of these to use with a similar chainring setup and 105 dual-STI brifters, but I have not yet installed it.