Hello Thibault,
Implement Expand_EntitySet where u can send your inputs as filters and get all those those table as output.
Create Entity for each of those output tables. Also Create Entity holding your Inputs as well.
Once u do this create association & navigation between entities with appropriate cardinality.
Implement Expand_EntitySet method and get all ur inputs as filters inside it and use it in ur logic.
Also send back the navigation properties to the expand clause table.
With using $expand in the url u can get the output tables.
Please refer the below which will help u : With this u can try accomplishing your scenario.
Implementing Expand Entity/Entity Set
Regards,
Ashwin