Please don't suggest pinning a publicly-trusted intermediate. The CA may change which intermediate they're using at any time for any reason with no warning, and then the app which pinned that intermediate is hosed.
You should probably pin the highest certificate in the chain that's going to stay current for as long as possible. Or, if the goal is just "I don't want people snooping around in my app's traffic" rather than "I want to protect against a rogue CA being used to hijack my customers' traffic", reuse the private key in the CSR and pin that, it'll get the job done.