You're getting ahead of yourself to a degree. It's not so much a question of importing complex un/subscription info as having a place to put it. You have to figure out how you're going to manage subs in Marketo (beyond the default Unsubscribed boolean field)
Once you figure out how you're going to store the info in Marketo -- timestamp or boolean fields, program membership, JSON field -- then importing it is easy.
However, Marketo will only remember the Unsubscribed value if a lead is deleted. If you want to preserve the other values for later, you'd need to export them and periodically reimport (w/existing records only) or call out to a webhook on lead creation to get supplementary info (my preference and how we manage giant suppression lists).