Hi Snautzer,
Very interesting theory you are coming up with.
I do not know wether the line could have broke from the glider or from the JU-52, but if it broke from the glider, I can't imagine that this would result in any sirious problems for the glider, but if the opposite happened, the rope could as you say, have caused serious and irreversible problems.
So this could mean that the drag of the line could be enough to slow down the speed of the glider and make it loose height and stall......
Thanks for sharing this theory with me, Snautzer
Warmest Regards,
Flemming