I think the premise of your question is incorrect. It assumes Haiku cannot be both useful for legacy compatibility and innovative in building new features and services on top of this base.
Personally, I won’t be spending any time worrying about 32 bit support or BeOS app compatibility in what I do in the OS day to day. (Although I’m sure people will want the Paladin IDE to be able to build 32 bit BeOS compatible apps…)
Whatever we add though will have a maintenance overhead so we need to be sure it’s worth the effort. Certainly ensuring existing groups’ efforts work well together rather than duplicate functionality is a good thing (Think Koder and Paladin IDE here - I have no real interest in adding YetAnotherCodeEditor to Paladin).
I’m sure there are a group of functions that we could add to an API on Haiku to benefit all app developers and users of those apps. As an example, someone mentioned adding scripting support to apps for Hey. Well, is there a way of making that much easier so it’s “on by default”? (E.g. automatically export all Menu Items as scriptable integration points, or similar for BMessages being sent to apps)
Replicant samples and recipes may also be a good way to expose value-add services to users without a lot of additional code bloat and associated maintenance cost.
Building all this in to the Paladin IDE so an app developer just has to write purely unique code for their app would be good. So I write a clock and notification app, but automatically I have replicants for a clock and upcoming events, and hey scripted commands for adding/listing/getting/removing events.