I am only starting out but I have been experimenting growing mushrooms in woody plants that I can't find any information about. so far I have yet to be able to harvest anything but there is for sure mycelium growing that is visible. I think if you have a little money to spend then you could cut off a smaller part and experiment. hopefully someone who knows more about ficus will have better information but if not I think it is worth experimenting.
I think you need to think about what type of climate you live in-where do you live? Different fungi grow well in different places. I would do a search about ficus as a substrate. An aggressive mushroom like oyster or turkey tail would grow well where I live.
Thanks John. I appreciate the response. I live in Southern California. So its a nice climate here for a select species of mushrooms. I can't find much research on google about using ficus as a substrate.