you don't need a proxy if you don't mine at nichhash, because (1) they run port 3334 for sha256, (2) you need to define a price
simply use CNAME for those 3333 pools
miner config pool1 [<your-hostname>.ddns.org:3333] -> DNS Alias (CNAME) map to sg.kano.is for example
sorry for sharing an unworkable idea, changing cname won't immediate switch pool unless there is a network failure occured thus break the current session and reconnect
run a CentOS 7 box as a Network Address Translation router 100% works that I've been tested for a week
miner pool1 config [<your-noip-hostname>.ddns.org:3333] -> your CentOS box ip
since my hosted S7's are runnning :3333 and :3334 i need to do 2 port translation rules, 139.162.5.112 is sg.kano.is, and assuming your firewalld is enabled active zone is "PUBLIC"
firewall-cmd --zone=public --add-masquerade //enable NAT
firewall-cmd --zone=public --add-forward-port=port=3333:proto=tcp:toport=3333:toaddr=139.162.5.112
firewall-cmd --zone=public --add-forward-port=port=3334:proto=tcp:toport=3333:toaddr=139.162.5.112
to switch pool simply reboot CentOS box and configure the new "toaddr=x.x.x.x"
hash at nicehash you still need a proxy to set price
my 4 x
S7@4.73 have been down for 13 hours