I mocked up a better workflow for video in a mastodon mobile app. I'm not a developer, just a mobile user who wants to stay in their fedi app of choice (currently Moshidon) while enjoying multimedia content and not get booted out to a web browser every time I want to watch a video or listen to a podcast. I still have no idea how difficult or feasible it is to actually implement this concept.
I think it's very important for fediverse mobile apps to support audio and video streaming to integrate with platforms like Peertube, Castopod, Bandwagon (once that gets going), etc.
I also ran into that issue the other day. Did you file a feature request for that? If you didn't I will. In general though I really like Moshidon. The video player functionality I want is not available in any mastodon client app except for Fedilab technically, but its implementation is still very primitive for now.