A 5 second period of invincibility after randomly TPing to a world would be good. Just been spawned next to a creeper, instantly killed, and lost all starting items in regrowth and have no real way of getting started again as there is no reset command.
I really like this idea, /rtp sometimes throws you into blocks and suffocates you. This would be prevented by 5 seconds invincibility.
I'd also increase the login invincibility to last unthil the player moves to prevent people from getting killed by random stuff on login.
I think that would be very useful because of the long load time after logging in, but I think it belongs to another post.
personally give them 10sec invincibility until they move, especially if afk for 7+ mins i got knocked off my island by a random zombies on AS2 and lost a wand I tried very hard in earning, i was afk to do chores