No NSFW content in public theatre rooms.
I like the arcade/games room idea. but disallow vapes in theatres as they become a nuisance fast.
Sandbox currently uses an addon called 'wardrobe' which allows hotloading of most playermodels from the workshop when the player 'requests' a model, meaning players will not have to download any models when joining. (seeing these models is toggleable clientside, and there is model blacklisting for admins)
Easy to implement
I suggest no guns at all. From my time on sandbox, it is next to impossible to enjoy a video over the sound of someone needlessly unloading magazines into the screen or your face.
To tie all of the new servers together, perhaps implement serverwide announcements in the text chat that there is an event about to start on the sandbox/darkrp server, with enough notice time for players to connect.
Take a leaf from the sandbox server and allow players to use the PAC 3 editor addon, for full player customisablity.