We surely want to give it a try with the right person. The main point that we are still not sure about is what kind of questions we should ask him to make sure that he is a good fit for this. If this was a developer position, I would know how to evaluate him, but I have no idea about what it takes to be a good marketer. I guess we will need to let him try and then see how it goes.
I was lucky enough to have been a mentor for a pre-accelerator start-up last year alongside someone who proved over a few months to be an effective marketeer and manager. That start-up foundered for all sorts of reasons but the marketing person is now a key part of the team for my current start-up.
I suppose I am saying - the only way to find out is to give them a try. If someone is genuinely enthusiastic about the product and has some positive ideas and the cultural fit feels right then why not?
I am not a people person and never been to that line (marketing, hiring) so it feels a bit different and new altogether. At some point, this has to be done, so why not now.
With a low risk then you can offer a new founder up to a third of the business. The challenge you should set is to "find the customers". This may well involve at least a partial "pivot" - and that is where the extra work comes in.
You don't have to incorporate and formalise the arrangement until the new revenue stream is located and at least partially proven (you can just write and sign some sort of informal agreement). Once you have a clear view of your customers, what they want from the product and how much they are willing to pay then you have a business and a proven marketing founder.