You can use any instrument, as long as a broker supports it and offers an API or MT4 for access. Volume, interest etc. are just a data curve. They can be added the same way as an instrument and accessed with the asset() function. The prodedure is described under "Data Import".

We can not publish roadmaps because most new features are paid by customers. So the release date of a feature does not depend on us. But you can see under "What's new" which features are planned for the future.