(add-to-list 'tramp-methods
'("sudosaba"
(tramp-login-program "ssh -t saba ssh -t sudosaba sudo ssh")
(tramp-login-args (("%h")))
(tramp-async-args (("-q")))
(tramp-remote-shell "/bin/sh")
(tramp-remote-shell-args ("-c"))
(tramp-gw-args (("-o" "GlobalKnownHostsFile=/dev/null")
("-o" "UserKnownHostsFile=/dev/null")
("-o" "StrictHostKeyChecking=no")))
(tramp-default-port 22)))
alist 足せばいいだけだった。別途 .ssh/config 設定とか必要な場合もあるだろうけど。