Include additional category field in registration

It would be nice if fields related to an additional category are taken into account when registering for an event, to make it possible to fine tune fields and categories (parameter Assign Custom Fields to category instead of to events = yes)

Example we have the following categories, fields
name, email, phone (always needed)
category competition: ranking, federation registration #
category wintercompetition: winter competition level (junior 11-12, senior 35+), winter matchday (monday, tuesday)
category summercompetition: summer competition level (junior 9-10, junior 11-12, senior 35+), summer matchday (wednesday, saturday)

The requirement is to model a "start summercompetition event" with category competition, additional category summercompetition
This could result in the following event fields

name
email
phone
ranking (competition)
federation registration # (competition)
summer competition level (summercompetition)
summer matchday (summercompetition)

Thanks