if you unlinked your PSN account from your current EA account it is linked to, you would automatically lose most, if not all, of your progress. This is also explained in the article regarding unlinking accounts.
So even if there wasn't the one account in a lifetime limit, I would recommend not relinking your accounts as this would cause a lot of issues for your PSN account.
yes, simply don't unlink the accounts. As long as they're all connected to the same EA account, they will be merged once you get the cross progression prompt.
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