These are all very good points
Uh what?
If you run a Lvl 10 quest at 13 it won't break your streak anyway!
If your friends are too high for BB then again neither your nor your friends streaks will be broken!
I will give a couple of examples though where I see this being used:
1) Iconics and Stoned Characters going into Epics who don't want to have to go back and farm out the Heroic versions on Elite first so they don't break their streaks when running EN.
2) Many Epic Players who want to run mainly ENs but keep their streak intact for the inevitable TR.
3) End-Game content {Raids} that's mainly run on EN - You can't run it on EN or EH because it would break your streak, You can't run it on EE because you're not capable of leading and there's never any groups up!
I read in in-game chat today that one player would be happy with this change because he's never run MoD because it would break his streak and now he can!