Few might remember that Alpine was originally based on Gentoo. You can still find some old references (like mkinitcpio hooks for fbsplash).
Possibly the biggest hint is /etc/apk/world, the "worldfile", or the list of explicitly installed packages. It's even the same verbiage Gentoo uses (albeit a different location - Gentoo stores it somewhere under /var)
S6 and the Obarun-developed wrapper 66 Suite are really really nice. I hope more distros pick it up.
Not by s6, but s6 author may introduce a new init for alpine
Either way, I've been watching that s6 project for a couple years now and am looking forward to when that happens. Is there any progress on that front? I hadn't heard that the replacement might not actually be s6.