Sending routes or track directly from BaseCamp to your zumo will probably not work, but you can save them to a GPX file on your Mac and transfer them manually with OpenMTP. You can save the files to iCloud, so that they are available on your iPhone. From there you can transfer them wireless using the Tread app.
I don't think Garmin is going to update BaseCamp anymore, the consequence is that it will not run on the second next version of MacOS.
When Garmin says BC does not "support" the XT and XT2, it actually means that not all activity profiles or avoidances are supported. I have been using BC with my XT for complex route planning for a bunch of years and many thousands of miles. It works just fine as long as you check your routes once they are in the XT and use tracks to verify that they haven't changed due to recalculation.
BaseCamp tends to crash when I connect an MTP device.
The activity profiles an avoidances in BaseCamp have never been completely in sync with any device Garmin ever made, so that is not what Garmin meant with that remark...
So, unless there is a way to shut off recalculate then I am SOL with Garmin and the search continues for an iOS based mapping solution. I'm flabbergasted that no one, most notably Garmin, doesn't have a solution for mapping out your own route and using the GPS for guidance and allowing on the fly changes. I'm sure it's an exceedingly simple matter for them to implement, they just don't. As you said, you can meticulously modify a route that it forces on you only to have it recalculate along the way and need up the entire thing. When I tried to use a promising solution years ago I discovered, through their own admission, that the software designers don't talk to/review with the hardware guys.
I need to go from NH to SC on interstates, keep options open for checking out various sites along the way, avoid places like DC and (esp) NY city. I can't be the only one who wants too do this from time to time without jumping through endless hoops to keep it from redirecting you to whetter you don't want to go. Seeing waypoints is not much better, one error in seeing them can have you many miles off course if you don't catch it in time. If you don't realize what it's doing it will take you on a merry chased trying to get you back to the missed point.
I can use my iphone and a paper map if I want to go through that much hassle.
I'm a little confused by your reply. You can definitely turn off recalc in your zumo. BC can indeed be used successfully to plan your NH to SC route (I just got done putting together a MA to NC route which avoids NYC). Not sure what you mean by "seeing waypoints," but if you mean placing them on your route, yes, you do need to zoom in to avoid inaccurate placement that can indeed screw up a route, but that's true of all mapping software.
