It’s true that inline conversions require boilerplate. But they don’t need to expose safety holes since the base trait (MyInlineConversion in the example) can be sealed. On the other hand, Scala 2 does not have inline at all, so I don’t see a regression here.
Path dependent implicit conversions are indeed not supported. Maybe we can introduce a Conversion class that allows dependent typing at some point. Or maybe that does not work and path-dependent implicit conversions are dropped for good. I personally don’t lose sleep over this, since the use cases seem to be questionable designs anyway. I would probably object to inventing a special language feature for this; that would send exactly the wrong signal.