I love your proposal! The added/moved events would be a good way to mix things up. I'd opt for a few different things though:
Find a way to limit attendance to the Passholder Preview. It being more hectic than Opening Day is absolutely insane and the associates who are able to show up that early in the season don't need all of that. I think Dollywood might've required a reservation for their 2026 preview day?
Opening Day: Keep the size and scope, but ditch hosting any shows in the Carousel Pavilion. Anytime they host a show in there means that the Grand Carousel's band organ gets turned off and replaced with a recording. I feel like the oldest ride in the park should be able to keep one of its defining features every Opening Day.
Brew & BBQ would be nice to have (especially if it goes well at Canada's Wonderland this year)(and as long as Cedar Point doesn't get jealous of their sister park down south getting a similar event) though I'd contain it to Rivertown. Put the BBQ equipment and a lot of picnic tables next to the Tomb Raider building (where Slaughterhouse's queue partially goes) if a large area is needed for that.
No Viva La Fiesta. I'd prefer KI either get its own event or its own version of an existing event. Possibly an "Island Nights" event, or a "KingsFest" (bad name, but the premise is it being a celebration of the park), or something else that's more unique than VLF.
I've posted my wishes for Haunt elsewhere on these forums, but my thoughts can be boiled down to a) more + better mazes, and b) more + better shows.
As for entertainment I'd just like to outline what my dream scenario would be:
Shows that run from Memorial Day weekend until the end of daily operations. No big venue goes dark for more than 7 continuous days during that time. Maybe 14 days if there's a second show that goes somewhere.
Big Venue = KI Theater, International Showplace Theatre, the Bandstand, and the Festhaus. Preferably I'd also add two new venues with one going in Rivertown and the other going in either Coney Mall or Action Zone.
At least four showtimes each day for each entertainment offering. Being the "family park", Kings Island should have stuff for the whole family to do together for the majority of the day. Currently there's the Grand Carousel, the train, eating, and maybe 3 shows if you visit at the right time of year and if all of the shows aren't happening at the exact same times.
I cannot express how nice it was to see that Dollywood had showtimes that started a various times from 11AM to 6PM. If Six Flags doesn't want KI to compete with Cedar Point's coasters, then they should see about having it compete with Dollywood's entertainment.
Get the stunt shows out of the International Showplace. Let that stage breathe again and put a KI-run show back in there.
Maybe some small stage shows (I saw a small stage set up between Soak City's First Aid and the shop that's right there, so I wonder what that's for) like we had in 2021.