This is just the command to do precisely what you said, make everything type messaged to every other player in the room like a chat room. This one command will basically make a Questnet Chat room that you could run for an indefinite amount of time.
command <#input[userid]#> {
for each object in <#quest.currentroom[userid]#> if property <#quest.thing#; netplayer> then {
msgto <#quest.thing#; $name(%userid%)$: #input[userid]#|n>
}
}