Power Pivot :: Dynamic Slicers Without Two Way Relationships?

So, after my last post where the issue came down to my model, I have redone my data sources as a v.2 model and split out into traditional dim/fact tables. I have 2 fact tables a few dims that are shared between the two facts and some dims that are only on one fact.

In my old model I was doing most of this de-normalisation in my sql queries to produce the fact tables (and the two fact tables were related together).

In v1 I used to get a much better context-aware set of slicers as they were directly connected to the fact that the visualisations on the page were relating to. As I selected a slicer, any other slicers items that were no longer possible would disappear.

This is no longer happening with this star-schema method. The old way was better from a user perspective. I had to remove some "both" cross filter directions from the relationship model due on the dims that were shared between both facts, so they are only now Single. I wonder if that has any bearing on this but even if it does, I don't see a solution from this angle.

I guess the only idea I have would be to create calculated measures/columns (probably columns) to materialise the interesting dim values into the fact table but this seems a bit of a time consuming process and as I don't necessarily know in advance which slicers the users may want to use, so it feels like I almost need to add all possible dimension attributes in each fact table... ?

Here is my relationship diagram. In my testing the slicer updates work ok if they are on a 2 way relationship but not on a Single way relationship.

In my case my 2 fact tables are really related (SchemeParticipantResult is a parent of ParticipantMeasureResult) but this then breaks the traditional Star schema that I was advised to follow before.