Yeah I too hate small niggles and bad design, not just with Mazda but all modern "design" I sometimes feel that people dream something up and just try it for a laugh; no product testing in real life.
Having a saloon I haven't encountered the tailgate issue but I wouldn't stand for stuff like that, can the system be re programmed by Mazda dealer to bypass/override this? I fail to see the attraction of button stop/start buttons, seems to have become something of a fashion statement, ditto with electric handbrakes-- pointless, I have a mate with an A6 and you can't change the rear pads without the engine running to work the electric handbrake and allow the pads to be removed, classically poor design! I guess it's cost cutting with most things.
Rusty bike- try looking for info online re the USB, the latest software update seems to improve this and apparently the way the stick is formatted has an impact too, this is hearsay but a quick search with Mazda and usb etc will show links and threads if I recall related to the M3 but the basics will be that same.