Yes, the passing of Carl Weather will be hard to predict how the series pivots with Grief Karga being written out of the series, but remaining out there in universe like Cara Dune or if they will actually say he passed away in story as well.
I like EddieDeans structure proposal and I am eager to see how it plays out. I do need to go back and watch your original book five when I have a moment as it has been a minute. I am all for extending the Grogu and Din separation as much as possible, as Jon Faverau said in an interview I believe they were supposed to be apart for three years and honestly it does not even feel like three weeks in the original show.
As for trying to make Boba part of the retaking of Mandalore. I believe there are a few directions you may be able to go with the use of AI or depending on your/ this community’s editing skills with visual inserts as well. I know Jar Jar Bricks is amazing with AI.
You may want to connect with one another, as I think you could maybe use Din in his ship (helmet on obviously) conversing with Boba over the ship’s speaker using an AI convo for both men. You could have Boba saying he can’t make it unfortunately as he has his own problems putting down a gang war in his newly won territory on Tatooine (adding a mini hologram of Boba with helmet on would be even more ideal; think Palpatine during order 66 scenes with Plo Koon). Another more ambitious approach would be adding the Slave I to the fleet the amasses during season three to retake mandalore. The ship with a few Boba lines could really sell he is there helping. However, this may be out of the scope of your project, but I know it could be pulled off with the skills of people within this community. Just my two cents, let me know what you think!