Alias or alternative ISO code lookup for 1 country

I am trying to implement an integration with multiple API’s that use old or alternative ISO lookups for certain countries/territories.

I am using the country list from frappe/erpnext in a custom doctype as a drop down and the issue I am having is, that some of the ISO 3166-1 codes do not match with the ones from the receiving API’s and therefore the request gives an error.

The ISO 3166-1 codes in the provided Country List from frappe/erpnext are up to date, but the receiving API’s have some countries and territories that are outdated and have not been updated. I am trying to be able to add an additional country code in the Country List so that they are passed as an alias in case the first country is not found in the receiving API.

Some examples:

Country Name - API 1 Country Code - ISO Country Code - API 2 Country Code

Curacao - XC - CW - CW
Bonaire - XB - BQ - BQ
Saint Eustaius and Saba - XE - BQ - BQ
Saint Martin (French) - XM - MF - MF
Sint Maarten (Dutch part) - XM - SX - SX
Saint Kitts and Nevis - XN - KN - KN
Saint Barthélemy - XY - BL - GP (GP because its still marked as part of Guadaloupe which it no longer is)
Canary Islands - IC - ES - ES

Does anyone have some suggestions? Also my concern is that any modification may break upon an update to frappe/erpnext.