How do you know the variant? If the user is just using an "import csv" on the web form, how do you know? You can't even ask the user because it's not even clear they'll know, it's just the CSV they got from Jira, their other vendor, whatever.

And then the other direction is even worse, when you emit a RFC compliant CSV and the other party complains their batch job chokes on "" escaped quotes, etc., so you end up holding a mapping of clients -> "CSV" formats