HPM-Board

I noticed there is still some empty space and thought of two new ideas for them. I could build these in creative if necessary.

1. Redstone Trading Machine
-Not too large -Allows for players to safely trade
-If either player doesn't want to trade they can back out
-No accidental takes from other passing players
POSSIBILITIES
-Close to spawn
-Exterior of the building

2. PVP Arena
-A decent amount of space where players can fight each other for fun or pride
-Could look like a Japanese Dojo to practice combat
POSSIBILITIES
-Inventory Save
-Starting kit for fairness (Iron Armor/Sword/Bow/Arrows)
-Has a safe area to heal up

Could I build a roller coaster