CR2's are safe if you pay attention to them... When used in series they should be checked and paired by their voltage ratings...
Don't overcharge them, don't try and get every last vape out of them, and discard them at even the slightest sign of issue...
CR2's have got a bad rap and it's mainly from user error.... They are safe to use IMHO if you treat them with respect....
Also, from what I can tell, it's the blue CR2's that have had issues... I don't recall seeing any issues with the green ones... (yet, as I am sure someone will use them improperly / irresponsibly)
My .02
Kris