My dream ride would be a Intamin Giga between Ka and Toro since Nitro already has an amazing long out and back B&M layout.
As far as open spots go, there is a lot of space between Cyborg and Spin Meister's old ride pad for some flats or a small kids area like DC Super Friends. Also depending on how JDC's new queue and path turns out, along with the removal of Safari Tours, the Safari Kids/ Looney Tune Seaport area has room and is in dire need of a major retheme.
Then, across Wonder Woman and next to Dark Knight where Chillers top hat and cobra roll is; there is room for an Endeavor or Air Race or even a Zamperla Wave Swinger to give the area some family rides to compliment Justice League.
Over in the Golden Kingdom I would love to see Balin's Jungleland return with the incredible theming and Tigerland Treehouse. The pictures of the climbing structure was but with the pandemic that doesn't seem like a logical thing to do. A section to view the baboons or expand the Safari Discoveries would better suite the section.
The Lakefront next to Joker is all open space but I feel that a ride there would ruin the peaceful atmosphere that's behind Yum Yum Cafe, although something like Catwomans Whip coming to SFSTL would fit nicely next to Joker.
As for the boardwalk, there is a lot that can and needs to be done, first off removing the simulator building and moving the go karts (or removing them) across and behind Twister can free up a lot of space for a ground up coaster like a premier Launch or RMC I-Box like Goliath at SFGAM, or something even like Iron Gwazi would be epic. Also the board walk needs a flat or two, something in front of Green Lanterns Dive Loop ( Where Space Shuttle used to be) would fit a nice addition and a replacement for Twister because lets face it, I'm surprised that the ride has lasted this long.... with a water ride like SFOT's new Aquaman or something.
Last but not least, Rolling Thunders former footprint could be replaced with endless possibilities. I would love to see the space saved for something epic like I mentioned earlier in this post for a Giga with extreme ejector airtime like Skyrush on steroids or something a little more realistic like the east coast version of Twisted Colossus or East Coast Racers. (Who cares about Zu's queue, I'm sure they can reroute it if they REALLY need to).
Finally, the park really needs to step up their entertainment offering. Even starting with small things like street shows at Liberty Gazebo, Runaway country and magic tricks as guests walk by. Then have at least one show in the parks venues especially the showcase which has heating and a/c.
In my post, I basically just mean to discuss available plots of land in the park new attractions that could be added as well as what kind of new rides we could see based on the company's recent investments for all their parks. The next addition to the parks lineup I really think will be a new kids section since the park removed LTSP minus Taz Tornado for a new major coaster. I can see something like Dc Super Friends next to Cyborg and JLBFM coming with relocated rides like RRR, Daffy's Deep Sea Diver and Pepe Lepew (especially with all the controversy going on) all being rethemed plus maybe a Larsen flying scooter or a new ride being added with. Another possibility can be a newly rethemed kids area replacing safari kids with something like Bugs Bunny Boom Town, an expansion of Bugs Bunny National Park and/or maybe even a return of Balin's Jungleland in it's original form with hopefully maybe a new show or two included would be a nice treat. We shall see what happens!