I am guessing the differences will be subtle, and most of the general
behavior you desire will remain the same.  You may be able to get a way
with a "sed 's/sv\ /s6-sv\ /' <old-script-name >new-script-name" on some of
your scripts; give it a try, what could it hurt?

Also, for those systems not running CentOS, what are you currently using
for init + service management?