1- For activity points, now with the lack of players, nobody or really a bare minimum of players play 3 hours to get their activity point. In my opinion is way too much, an hour should suffice.
2- I don't know about how long does a streamer has to stream to get his/her coins, but that is one of a fair way to do it, at least an hour too since not much people do watch gunz streamers nonetheless.
3- Weekly competitions, as in Clan Wars and Duel Tournaments? Those, aside VIP event as well are other fair ways to win coins.
4- For Rebirth, a player should be able to Rebirth anytime they get their level 99 without limitations of time they can do it... I don't even see there's a timed limitation on that...