I don't really have a specific train in mind for this suggestion, it's more of a generic suggestion for all trains running with the older PKP IC livery coaches, and mainly the longer ones.
When there is a shortage of 2nd class coaches, some older 1st class coaches appear to be "downgraded" to 2nd class. So on longer trains with the older coaches perhaps a few 1st class coaches could be mixed into the composition.
(photo just for reference)