Job title problem

I have offered to volunteer my time and expertise PRO BONO to research and write for a small think tank, and after reviewing my cv they enthusiastically agreed. I said we would have to agree on a designation (I want to be able to list this on my cv too, naturally) and they said they are open to my suggestions and also suggested a first project.
So I agreed to do the project, a writing piece of 1500 words that will entail a fair amount of research and analysis. I also put forth the suggested title of policy analyst - remember this is all pro bono! They wrote back saying that they want a draft of my paper first before they can accept the title.

Now I am unsure how to proceed. On one hand, I suppose i can understand that they want to check that my research and writing standard is high enough to merit association with their think tank. On the other hand, they have already reviewed my CV - when people are offered jobs, it is without a prior first draft that they are taken on. Especially as I am willing to do all this work for free, I feel they should be willing to agree on the title now. I am, by the way, a holder of an MA, not someone fresh out of school.

How do you think I should proceed? Is it reasonable to do it their way - write the first draft, and then they see whether they agree to this title; or tell them that I am unable to put in so much time and effort without even a title, even if this is voluntary? Please share your thoughts.