For the moment, installed Xubuntu 18.10, upgraded it to Disco, installed ubuntu-unity-desktop from the PPA, uninstalled xubuntu-desktop and most of xfce apps. I kept some, like the wallpapers and icons.
Can build an iso from the installed one, but it is too early.
If your PPA can be kept to a minimal, without as much as possible gnome shell stuff, installing over Xubuntu would make it much more snappier.
Idling with only system monitor open. Memory 760.5 MiB (797.44MB).