Hi Mark,

It's true that the writing niche is a big one but you didn't say what part of the writing niche it is aimed at.
Copywriting
TV and film scripts
factual
storytelling
reporting
sales copy

to name but a few.
You would need to check the competition in the area concerned and work out if you can put together a similar product like someone who is doing it already. Basically, reverse engineer what they are doing and work out if you can compete.

You would also need to identify people with lists in your niche and guage if you would have a chance of doing a deal with them.

As Chris says, you will rarely get the big list owners to promote an unknown product or person. This is why it is important to be an expert in a given niche. Maybe the person who created the product may have enough weight to be able to get leads.

Hope this helps.
Martin