Barnoe,
For what it's worth, I updated the map on my Nav V to match yours but left the map on my Mac as the old version. I then dragged the route file straight into my Nav V, from within BaseCamp itself. Not surprisingly, just as you did, I received a warning that the route was created in different versions of the maps and that a recalculation would occur before the routes were sent from my Mac to the device. The recalculation took place, I could see Basecamp making the recalculation between each shaping point in a pop-up window. I then disconnected the device from my Mac.
My device then prompted me that there were new routes available, would I like to import them? I said, yes. The device then imported each of the four individual routes and the complete route (five routes in all) into Trip Planner, just as it should do. This took a little while as it has to take the data it has received and convert it into a form that is useable on the screen. The five routes, installed into Trip Planner perfectly, just as they should. I did, as I always do, then summon each route up and compared each with the version held in BaseCamp on my Mac; they matched. I am confident that each would run perfectly, should I have been sitting in Luxembourg.
I then went back to my Mac and updated the map to the latest version. I then deleted the old map, as I see no point in keeping old maps. I then asked BaseCamp to recalculate each of the five routes, which BaseCamp did for me. Each recalculated perfectly.
I then went back into my device and asked it to convert a shaping point or two (little blue dots) into via points (little flags) and via point into a shaping point. When changing a via point flag into a blue dot shaping point, the device gave me a warning that this would require a recalculation, would I like to do it? I said yes. Each converted perfectly, the route not changing as a result of the recalculation. I then changed them back, which worked perfectly again.
What does this tell us?
1. I use a Mac, not a PC.
2. BaseCamp is not the monster bods make it out to be.
3. It is possible to create complex routes.
4. It is possible and quite safe to allow recalculations.
5. It is possible to display and run complex routes on a Nav V and other Garmin devices.
6. You can change via points into shaping points and visa-versa, quite safely.
7. You do not need to use My Route. Not doing so, avoids bringing in other challenges to an otherwise smooth operation.
8. That I like Basecamp, my Mac and my Garmin devices.
Am I unique? I don't think so. Leedude (a regular correspondent in this section) does he same on his PC and, I think, uses an 'old' (but still very good) 550, without any problems. So it must be possible. Others do, too.