Well, I said not to have too much hope as I reported what OmegaMattman told me that it wouldn't be that seamless. But at least I did it for myself ;) and I can share it if anyone else is interested. Thus said, I'm sure I'll never watch it this way myself, I'll use each project's blu-ray.

And it's NOT seamless branching, it's only "cheating with the playlists" to recreate it, thus the pause when the BD player goes from one segment to another. I sincerely thought the pause would be longer. And I guess we can't afford Sonic's Scenarist to achieve "real" seamless branching.