These are some ideas for things I've come up with that could be added into the game.
Elevators: Vertical transportation for usage by both visitors and players.
Multi-station shuttle rides: Allowing for, e.g. a two-station Monorail able to act as a shuttle ride.
Jumps: Allowing for roller-coasters to be able to jump off one track and land on another without crashing; or to derail vertically and then to re-attach to the rail.
Reverse booster: A booster that launches the cart backwards for shuttle rides.
One-way brakes: Brakes that only affect the cart while it is moving forwards, and not backwards.
Submarine: A water ride similar to Swan Boats, but capable of going up and down.
Planes: A custom track ride that can change to any angle at any time and has no real track. Basically an air coaster. Physical max for cart length is 1.
Launch coaster: A coaster that launches at a velocity of 100km/h when leaving the station. Costs $2000 by default.
Circle coaster: A coaster that has a large, circle-shaped track of which the carts will randomly rotate around. The carts all exit the station at the same time, but act as separate carts. The carts remain in an inverted position at the station, and fold into a steel-cart position when leaving the station. If used as a shuttle coaster, the last 5 pieces of the track will convert into a 3x3x3 tunnel if possible, in which the carts will flip around and keep on going if they reach the end, preventing the coaster from crashing. Supports are only present at the station track.
Bungee platform: An enclosed 5 x 5 x 10 intense ride in where customers strap themselves into a bungee and bounce around. Has 4 seats and lasts 35 seconds.
Drinking fountain: A small, wall-attached stall that slightly reduces visitor's Thirst level. Sales are free.
Extended restroom stall: A 1x2 restroom stall that fits 4 people at once.
Queue path extension: A path that can extend the side of a Queue Path, allowing for intersections, two-ride queues, e.t.c.