This seems like a really odd thread. The game is built around jumping into the battles going on in your area. If you take away the jump in and out grouping mentality of the game it will just turn it into a completely different game.
I guess the developers could make a toggle option for players to keep people from joining their battles or have it so only their friends could join in but more than likely that would just lead to some other problems.
As far as people doing things on your friends list that you do not like, not to point out the obvious but that can be fixed by removing them from your friends list.
as someone said about multiple friend requests, i would like to have a feature that lets only journeyman and above to be friends with me. unless i request someone lower than that. i also feel bad that novices teleport to me when in marleybone. its ruining the game for them.
While I agree with some of the OP's post I don't agree with all of it. Sometimes there are too many people killing the same thing and there aren't enough of the monsters to go around. Should I just stand around and wait til you are finished? What if you jump the next monster that pops up?
I would love to see an option to either accept all teleports, require acceptance before a teleport or block all teleports. This would allow for soloing when wanted, but still allow you to keep many people on your friend's list without worrying that someone is going to jump into a fight unwelcomed.
Another thing I wish is that you couldn't teleport anywhere that you haven't already unlocked. My six year old is one of those followers and she has picked up quests all over the place that she can't reach (and frankly can't handle) on her own. I have tried to explain that she shouldn't be doing that, but she is six and waiting to finish a world is tough for her. I think it would be beneficial to make her wait. It would help her develop more patience and also spare some of those on her friends list from the intrusion. My husband and I have already decided to clear out her friends list although I suppose the players could just remove her if they are annoyed.