Only rule i can think of is using bugs to piss off other players. (not pvp btw)
Or sinking a boat in middle of ocean on purpose with other players on it.

Players should be allowed to go everywhere. As some skilled players can easy skip 1.st boss and go direcly on second by using a troll to mine for them, for example.

Players should also have their private portals. But you must share your cores with others (trading) for gold as some of them may be unlucky with dungeons and have a hard time getting off 1.st island.
Portal from 1.st island --) to black forest is fine, but more than this is newbie help :D

As for events --- Maybe a Lox race? I am sure you can build a racing road in plains.
(if you dont like plains -- deep north is empty)
Hunting challange -- player with most deep meat/tropys/hides wins gold.
Tropy challange -- players hunt for the rare monster tropys (werewolf one, ghoust in swamp one, icegolem one, big goblin one)
Stupid house -- build the weirdest building you can by limited materials on pile (must be liveable with fire and roofed)
Iron/silver challange -- find iron/silver without using detection devices (no you cant use hammer :D)