Well it looks as though some brilliant folks have indeed solved the
installer thirst for numerous distros, by creating a generic framework that
works with many linux distros.::  A '9999' version is in portage
(thanks!) But other versions are found in the overlays "eix -R calamares"
Calamares has one 'killer feature' on disk partitioning::
"Calamares is a distribution-independent system installer, with an advanced
partitioning feature for both manual and automated partitioning operations.
It is the first installer with an automated “Replace Partition” option,
which makes it easy to reuse a partition over and over for distribution
testing. Calamares is designed to be customizable by distribution
maintainers without need for cumbersome patching, thanks to third party
branding and external modules support." 
Best of all:: Calamares is purported to be very 'openrc' friendly!
For you kids, that's '420 friendly' :: very cool? That's actually
the literal, Klingon translation.....
Has anyone tried this out (calamares)?
If so, can you put your (iso) somewhere for wider testing?
It even seems our pals @sabayon have caught the calamares bug::