Here is my huge pack of ideas. If you have anymore, post em' here (sorry if this topic has already been posted)
-smooth out track
-add sideshows (carnival games where you win stuffed animals)
-add more Intamin coasters (stratacoaster, inverted coaster, rocket coaster) and a spine changing option. (quad-rail, tri-rail, & bi-rail)
-hotels(guest stay for more than 1 day and comes back)
-rainbow lights on all rides
-catwalks on coasters w/ their lights
-full control over track and supports (ie. the node system use in NL, which was said that it wouldn't be implemented in the game)
-overbanks, zero-g-rolls,etc
-more control over segment. (ie. banking amount, size of corkscrews,etc)
-park explorer instead of coaster cam.(what I mean by park explorer is something allowing you to fully explore the park as a guest would, by starting at the edge of the map, then walking using the keyboard to get to the park entrance, then walking through the queue, through the turnstiles, up the platform, to the seat, and then pressing a key to sit down. Harness closes, you can't get out, you ride the ride, get out the seat using the same key, go through the exit, on the path and to the next ride. The Park explorer should also let you play the sideshows, and buy items from the shop (food, souviners, on-ride-photos,etc) Also, park explorer should let you ride all types of rides, and choose your seat.)
-make track rail curves less jagged
-more flat rides
-should look like original (too late for that)
-custom additions (user-created rides and scenery)
-quick way to make above-ground tunnels (instead of having to use scenery)
-tunnel effects (i.e. fog, light flashes, etc)
-"company" mode (go around parks designing coasters like what B&M does, or a park management company chain like Six Flags)
-guest animations on coasters (raising arms and screaming w/ mouth wide open)
-moving clouds
-choice of backdrop (trees, water, or mountains)
-new and improved land tools (like muilti-tile mountain tool, and muilti-tile corner raise tool. Tools should be found in BOTH the park editor, and the scenario editor)
-creating rides and guests should be allowed in scenario editor
-get rid of unrealistic theming (like that serpent slide)