These are some suggestions I wrote about fixing some Scala porblems. It was written about an year ago, so, I don't know how it is applied to Dotty project. But I hope it gives an idea to language developers.
In regards to your first suggestion, unless I've misunderstood, this commonly goes under the headline of MyType and is discussed every few years. If there's likely to be any change in the Dotty timeframe I'd love to hear about it.