Infuse implemented code specifically for jellyfin and it uses jellyfin's own API. The only common protocol is dlna, but it's pretty limited and only really used on local networks.
That would slow down development and new idea down a lot, I don't think it's even worth considering. It's probably easier to implement it on Kodi/Infuse/any other clients.
> It's probably easier to implement it on Kodi/Infuse/any other clients
Yep, it's definitely easier to get third party clients to implement your protocol. Kodi you can write your own plugins for, Infuse... requires their devs to care about your implementation. Chicken, meet egg?
That said, I also fully admit I have no knowledge of your codebase, nor any knowledge of how extensive / complicated the jellyfin (or any other comparable media server) client api looks like, and I assume you have a better idea!