Thinking about the opening to TLJ, perhaps we could go crazy and break convention:
After the ‘a long time ago’, open on the blackness of space. A light appears in the stars, glowing red and getting larger. A beam of energy streaks across the frame, and descends on the world of Hosnian Prime. Sella and others look up in horror as the beam incinerates the planet. Cut to black.
STAR WARS
Catastrophe! On the eve of a declaration of war, the New Republic has been devastated by a mysterious weapon from beyond the stars.
Determined to complete their victory, the First Order has tracked the shattered remnants of the Republic fleet to the planet D’Qar, determined to capture General Leia Organa and the location of the last Jedi.
With not a moment to spare, Leia orders an immediate evacuation, desperate to preserve the last spark of hope for a return of galactic peace…
Also: Make it clear in the crawl for TLJ that the First Order is intent on capturing Leia instead of destroying her so that she can be compelled to tell them Luke’s location. This will require cutting some of Hux’s lines, but I think it would still track with the rest of the movie. Kylo intentionally avoids firing on Leia when he senses her on the bridge, and Snoke only decides to wipe out the Resistance after he has the location of the island from Rey.
This allows for the TROS scene of the planet destroying to stay in TROS as a visual reminder of what the mysterious weapon must have been. I also like that only the Emperor is able to actually destroy planets.
The plan of Palpatine comes into clearer view now. In TFA the goal is to corrupt Luke’s Jedi order with Snoke and kill Luke, and also corrupt the Senate. In this way he would win without ever firing a shot. However since Luke disappears and the Resistance is formed to find him, he is forced to send the First Order out looking. Hux actually throws a spanner in the works with his failed Starkiller idea, which turns the Senate to seriously declaring war on the First Order, and requires him to destroy the Senate and fleet altogether. Then with Luke’s death he feels able to openly declare his supremacy, not counting on Luke’s effect on the galaxy and the existence of Rey.