I'm obliged to Stephen Prior, Ray Cripps, and Robert Cole of the MH & Campers UK Facebook group for responding. From their information, it seems that:
1) the "indicate lane-change" IS standard on the Ducato, much as I described it on my Ford.
2) again like the Ford, the same stalk operates both the flashers and main/dip selection.
3) there's a control panel to the right of the steering column, above the footwell, which MAY (not sure) allow you to change the number of flashes for the lane-change function.
All of which still leaves us with a question: does your particular vehicle have an unusually floppy lever (which needs fixing), or do you just need a slightly different technique, to avoid accidentally operating the lane-change signal when you dip or "undip" the headlights?