Add new Cypher and or ability to prefer or negociate

My suggestion is maybe ridiculous, but the idea is to add the ability for two hosts to negotiate the cypher based on the cpu capabilities or admin preference.
Chacha20 would be nice to add, it seems to be faster then Salsa20 and gives a bit more performance on slower cpus even if zerotier implements aes not every cpu has aes-ni., like the Edgerouter-X, intel atom and some smartphones.