I maintain that expanding property wrapper attributes to types, even if only in the parameter position, is out of scope for this proposal. What you're proposing is a bit of sugar on top of this proposal that comes with a lot of implementation complexity and downsides that haven't been fully considered yet. It also doesn't change anything about the base model of property wrappers on parameter declarations, so nothing is preventing someone from proposing this in the future.
The APIs you mention already exist today, because the only way to pass property wrappers around is to use their type directly. There are deprecation tools for APIs if a better solution comes along.