the ability to have injection point has been there since forever (it was possible even in 1.0) yet the option you are asking for is lacking. I certainly haven't been there when/is the design decision was taken
Javadoc of InjectionPoint even mentions that it can be a parameter of an Observer method.
I'd say what you ask is a feature request material for CDI spec.
Not sure how user friendly would be any solution on Weld side, we could probably have something like WeldProcessObserverMethod lifecycle event with a method returning it but that's hardly friendlier than just going over the params as you suggested.
Also note that Producer#getInjectionPoints() is really only good for browsing them as you cannot swap them out with another. At that point, they are only used for validation purposes.