This is feasible, but really not recommended. You will create duplicates and form Marketing Automation, duplicates are quite close to the Evil All the risks you are listing are real ones, and you can bet you will end up spending significant money to cleanse your duplicates in a few months.
All you need to start working is that a "Status" field is created on Contact, with the same values as the Lead Status one.
Now, if you really want to make a lead out of a contact is to run a "sync lead to SFDC" flow step a force the assignment to a lead queue. Argh
Thanks. All the work on the Contact side is coming -- we will be creating a funnel similar to the lead side, but there is more work to be done in our systems before we can do that.
My concern is the same with duplicates, and I agree it is bad practice. I am getting a lot of push back on this -- from a practical angle, I am not even sure how to tell Marketo to create the duplicate? I think it will just get messy but trying to explore options.