I just think if Benjen isn't coldhands then there is no point to coldhands really if Benjen is doing all the important things coldhands would have. The similarities are just too much to ignore:
- lost member of the nights watch.
- half dead, cold skin, both presumably killed and brought back to life with dragonglass.
- cover their faces so we don't see who they are.
- both save brans life from the white walkers at the same point in the book.
If Benjen isn't coldhands, then they just cut out coldhands altogether and replaced him with Benjen.