After writing the MRSS Feed Update Utility, I've been busy putting together a conversion program to complement it. I've just released the MRSS to JSON Converter to convert an MRSS feed to a JSON ('shortFormVideo') feed. I'm also in the process of writing a JSON Feed Manager, but, that's still a ways off.
If you'd like to convert your MRSS feed to a JSON ('shortFormVideo') feed, please take a look at what I have put together.
FREE Windows desktop software for creating BIF (Trick Play), Direct Publisher (MRSS, JSON), and FireTV feeds @ https://github.com/rrirower. No programming knowledge required.