I think it would be really cool if Misskey’s specific federated features would find more widespread implementation across fedi software (for example the custom emoji reactions or latex implementation) but it’s difficult since most of the Misskey developers can’t speak English at all so I guess it’s hard for the project to actually collaborate with Mastodon or Pleroma (the two softwares for which these features would make the most sense to me personally)
Misskey also already has a prototype of groups and chatgroups which currently sadly only work locally on your own instance and is not even federated to other misskey instances but I guess it is planned to have it federate in future and that would be really exciting to have in general for Mastodon and Pleroma too since it would reduce the need of having alts if you want to talk about specific topics that only a specific amount of people is supposed to see without creating hellthreads or something like that for example.
Another really sad thing is that both Misskey and Pleroma have a Chat functionality that is not interoperable. Misskey is doing it in a way that makes a chat to a non-misskey user appear like a direct messages thread to them, but Pleroma’s chats don’t work outside of Pleroma at all sadly and since Misskey’s implementation makes more sense to me personally it would have been really cool if Pleroma would have used the same.
The other way around, Misskey is lacking lots of features from other fedi software that I really like, for example the “mute thread” button if you’re getting tagged a lot in a thread you’re not participating in or instance blocks on user level (if I am not mistaken it has instance mutes on user level at least right now but it’s not a perfect situation)
Also, it would be nice if Misskey would also have a MastodonAPI compatible implementation so that it’s easier to use it with a lightweight app or so that people that already developed apps for Mastodon or Pleroma could also easily develop apps for Misskey. The app-situation for Misskey is currently a mess and there is basically no real way around using it in a browser on your phone since otherwise you would be way too much limited in your functionalities.
Another really cool thing about Misskey is that it has an implementation for a Gallery that you can create albums in and stuff so you can post pictures without them appearing on your timeline. This feature is also currently not federated, but you can link to your galleries you want to show and local users can find your public galleries on your profile. It would be really cool if this feature would 1. get federated and 2. would also interpret Pixelfed-Instances like this since it would render the pictures in the same Instagram-like aesthetic that Pixelfed uses instead of having them appear as posts.
The language barrier is really sad tbh since Misskey kinda has so many features that it’s impossible to fully know about all of them since the documentation is entirely in Japanese and the few translators the project has are having problems keeping up with it, plus there are apparently also documentation software issues that make it even harder for them to keep up with the documentation, so it appears that that issue might get better in the future maybe, but currently it’s just really hard to get an overview about everything Misskey can do and how exactly it functions
If I had the energy and knowledge for it I would love to help out but all I can do is donating to the Misskey project right now, but it would be sooo exciting to see all those features fully functioning and federating and even interoperable with other fedi software!