I would like to see Mastodon get a little pressure to support more of the standard, and others to follow suit.
I was thinking the other day about building a Fediverse location-sharing app (like Foursquare).
The vocabulary is all there (Arrive activity at a Place object being the most basic), but would it gain any steam if Mastodon didn't know what do with those other activities?
People would want to be able to cross-post to Mastodon, but Mastodon would just ignore it all, as would most other AP apps.