Love what I see !
As you can imagine I have some difficulties with RxJS operators and I realize now that it can’t be. I need to work on that.
Ok I think I can manage to implement your code I understand the idea.
But now, you make me hesitate, do I modify the API to deliver directly the necessary values or I make the forkJoin calls.
I think, I will first try to modify the API and then I will try to follow your best practices for the Ionic part.
Will do right now, besides I knew it 
Thanks a LOT !
I will keep you up to date when I fixed the issue.