Recommendations to Create Entity-Specific Models with Nested Hits/Documents

For accessing full documents you can to use a scripted_metric aggregation, the ootb aggregations work on single fields, not documents.

Top hits/metric won't help you, as you still need to collapse the entries into a document.

My advent calendar post from 2019 does collapsing the way you describe it, it is written in german, but maybe you can use in-built browser translation or a web service to translate it: