I for one, always build tall bases so I can place ziplines at the top.   There are many ways to go up in the base: Grass Stairs, Ramps (roofs), ladders, Bounce webs, acorn stairs.

As I tend to build further up in the base upwards of 9-10 floors, it gets frustrating to bring the pallets all the way back down the stairs.  I usually just start putting platforms on the outside of the tower and fall onto them, but those are not very aesthetic.

We need slides that you can make out of stems/grass; straight and curved pieces.      Plus I think they could be quite fun and something to put before ziplines but early game.

Now if we had pools, could put one at the bottom...

I would absolutely love to be able to build slides. It even fits with the fact that our characters are kids. I agree that if we could have both straight and curved slides that would be ideal. I'm sure straight slides would be easier to code, but with tall bases you'd have to build them fairly far out, (assuming we can't adjust the slope and that these pieces would be similar to the roof slopes), so in some areas  being able to add curve piece or a corkscrew slide, (like the spiral stairs), would be better due to space.