Let me try this game too.
I'd definitely take the 5ed core, for the sake of the spell guidelines which I think are more consistent than previous editions and to some extent the xp rules which I find fairer and more complete, and the book rules although that's only a minor improvement over 4ed.
I think I would pick a random 5ed tribunal book. Setting up a saga without a tribunal book I find awfully hard, but any tribunal works fine I think. Some of the 4ed tribunal books are good too, but they create some inconsistencies with 5ed core.
I see the house books and Cov come high on many lists. I agree. Cov is, in spite of many flaws, quite critical to flesh out the covenant, which is after all the most important character. And I would not want to play a house without having the relevant book either.
Potentially playing with people new to ArM, those five would definitely be my choice. Playing with more experienced players, I might argue differently, relying on much of HoH to be know.
I would miss RoP:M and RoP:F, and I would have to invent something rather non-canon, but I can live with that.