I share your hesitancy about Vader appearing to show him a vision of the future, though it would be ambiguous at best; was Vader trying to warn or dissuade him from being involved in firing the weapon?

Here’s a mockup of how the ideas expressed above might look when all baked together. I went with the former list of events, rather than breaking up Rey’s “force nap,” which I felt was very jarring. Honestly, it’s the approach that sounded better of the two! These are great ideas on paper, but I am uncertain if it will be totally doable using the finished film footage we have available.

https://vimeo.com/212386279
Password: fanedit

The cut from Fin and Rey turning to flee the oscillator to them climbing around in the snow is abrupt now.
The shot of the technician lady is abrupt, since her line cannot be salvaged; she speaks too fast to have it sound right to cut her off.
If the cutaway to Hux saying, “Prepare to fire” is a little jarring with the music, it could easily just be put right back where it originally was; it still fits perfectly there given this proposed order.

All in all, it’s a solid idea, but might not be able to be implemented well. And there’s a debate to be had about whether it is favorable to closely associate Han’s death with the Hosnian system’s destruction, and thereby Kylo Ren’s resolution towards the dark side and implied regret or incongruence. (In ROTJ, Luke took a bold risk by putting faith in his father, who redeemed himself and thereby allowed the day to be saved by taking out the Emperor and letting Luke go on to revive the Jedi. In TFA:R v1, Han took a bold risk by putting faith in his son, who resolved himself to the dark side and thereby ensured the day would not be saved because they were too busy with Kylo to detonate the explosives.)