I’ve always wanted more control in custom servers, like a /fly command and a /give command for items available in the current game (or just options for these on the /controls menu). Sometimes I’m hosting a cs and don’t want people buying items but need to give them a few specific items. This would also work in hub custom servers. This would be so helpful and unlock new possibilities in custom servers.
You should also be able to load into the game and change the map before the game starts. (thank you Bananamanyt5218 and AJtheOtter for improvements to this post)
It would be cool if you could go into creative mode to customise the map, like you guys have already said, but be able to save that specific customised world so that you can just load it in later. Was that confusing? For example: if you made a massive sumo platform, it would be cool if you could save that build and simply load it in next time so you have a pre-built sumo platform.