Hi Steven,
Sorry for the delayed reply. I wanted to touch on your question and address a few points. Not sure if I can give you a complete answer given the information above, but I can at least start:
What I want to do is include a point reference layer with a boundary layer...
Typically in ArcGIS Maps for Power BI, the points that you bring in would be based on the data that is coming from Power BI itself, and the boundary layer (polygons) would be a reference layer that you add in, as you would normally drive selection of points (and thus cross filter other visuals) by the reference layer's polygons. This work flow wouldn't work if your reference layer was constructed of points, since the selection would only be driven by those points from your data that were exactly coincident with the reference layer points.
Since this isn't making sense to me, there's a good chance here that I'm not understanding your use case. Would you mind walking me through how you would use the point layer as a reference layer? I'd like to understand and see if that's something we should explore in the product.
... does a paid for online subscription actually allow me to share layers to Power BI ...
Yes, if you have an ArcGIS Online subscription, you can author your own custom feature services with a single layer and then consume those feature services back in ArcGIS Maps for Power BI. As an additional point here...
... share the file publicly (which I don't understand why it has to be public) ...
The requirement to share your layer publicly is only the case if you do not have a private ArcGIS Online organization. As long as you're signed into your ArcGIS Online account in Maps for Power BI, your layers can be privately shared within your organization. Layers must be shared publicly if you aren't signed in since there is otherwise no way to reach those layers.
... another idea for future upgrades is to allow the visual to be used in the embed and publish to web functions.
We're currently exploring this, as we've had this request from a number of people.
... my first tests indicate issues such as place and point labels aren't coming through.
Feature services do need to be restricted to a single layer in order to be consumed in ArcGIS Maps for Power BI. If you want to share a cop[y of the service that you're working with (or a representative example), I'd be happy to take a look and see if there's some reason that your labels aren't showing up.
Thanks,
Josh