Ygtjki

I have a programme in bash that get JSONline files with several million of these object per line (See source)

 "company_number": "09626947",
 "data": 
 "address": 
 "address_line_1": "Troak Close",
 "country": "England",
 "locality": "Christchurch",
 "postal_code": "BH23 3SR",
 "premises": "9",
 "region": "Dorset"
 ,
 "country_of_residence": "United Kingdom",
 "date_of_birth": 
 "month": 11,
 "year": 1979
 ,
 "etag": "7123fb76e4ad7ee7542da210a368baa4c89d5a06",
 "kind": "individual-person-with-significant-control",
 "links": 
 "self": "/company/09626947/persons-with-significant-control/individual/FFeqke7T3LvGvX6xmuGqi5SJXAk"
 ,
 "name": "Ms Angela Lynette Miller",
 "name_elements": 
 "forename": "Angela",
 "middle_name": "Lynette",
 "surname": "Miller",
 "title": "Ms"
 ,
 "nationality": "British",
 "natures_of_control": [
 "significant-influence-or-control"
 ],
 "notified_on": "2016-06-06"
 

I have my JQ query that looks like this:

for file in psc_chunk_*; do
jq --slurp --raw-output 'def pad($n): range(0;$n) as $i | 
.[$i]; ([.[] | .data.natures_of_control | length] | max) as $mx |
.[] | 
select(.data) |
[.company_number, .data.kind, .data.address.address_line_1, .data.address.country, .data.address.locality, .data.address.postal_code, .data.address.premises, .data.identification.country_registered, .data.identification.legal_authority, .data.identification.legal_form, .data.identification.place_registered, .data.identification.registration_number, .data.ceased_on, .data.country_of_residence, "(.data.date_of_birth.year)-(.data.date_of_birth.month)", .data.etag, .data.links.self, .data.name, .data.name_elements.title, .data.name_elements.forename, .data.name_elements.middle_name, .data.name_elements.surname, .data.nationality, .data.notified_on, (.data.natures_of_control | pad($mx))] |
@csv' $file > $file.csv;
done

Which is probably hurting the eyes of many JQ pros out there - it is not efficient in extracting key:value pairs and if the provider happens to change name of a key my code wouldn't work anymore.

Is there a way to just flatten all the json into a csv keeping the keys as headers - with the extra difficulty that there is a list natures_of_control which has a varying number of entries (for which i used the pad function to get a rectangular result).