With all due respect. I think these consideration are not really relevant.
I used Sn60Pb40 solder, which has a melting point of 188°C (370°F).
There is absolutely no way I will ever bring these cells higher than 50°C during their cycle life, even if I pull very hard on them.
If you think about it one second, if these 18650 cells were volontarly brough to such high temperatures, they would probably vent (aka, go into thermal runway) waaaayyy before the solder would even start to melt.
So I think the idea that the solder could melt under high discharge rate is not a real life problem. It's irrelevant.
